Static Tests of Neutralization Potentials of Silicate

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Static tests of neutralization

potentials of silicate

and aluminosilicate mineralsJ.L. Jambor

Æ J.E. Dutrizac

Æ L.A. Groat

Æ M. Raudsepp

Abstract The acid-generating potential of rocksdepends on their sulfur content and neutralizationpotential (NP). Fifty-five ‘‘monomineralic’’ sampleshave been assessed for their NP contributions andfor the effect of compositional variations in mineralseries. For a threshold value of 20 kg CaCO3 equiv-alent per tonne of material, most rock-forming

minerals, including pyroxenes, amphiboles, feld-spars, micas, chlorites, and clays, will contributeinsufficient NP to attain or surpass the thresholdvalue. Although sample-to-sample variations in NPseem to be as significant as compositional variationswithin most series, the highly calcic members of theplagioclase feldspars yield more NP than the sodicmembers. The few high-NP results obtained fromsilicates–aluminosilicates were in most cases trace-able to contamination by carbonates. Olivine andwollastonite were exceptions, and the latter gave NPvalues approaching those of some carbonates. TheNP increases as the particle size becomes finer, but

normalization of the NP values to m

2

/g may yieldmisleading results; for example, a fivefold increase insurface area will likely increase the NP by only 5±3units of CaCO3 equivalent.

Keywords ARD prediction Æ Mineral series ÆNeutralization potential Æ Silicates–aluminosilicates Æ Surface areas

Introduction

In dealing with environmental aspects of the potentialexploitation of mineral and coal deposits, such as theongoing disposal of wastes at operating mines, the prep-aration for mine closure, and the remediation of aban-doned sites, it is essential to predict the geochemicalbehavior of the wastes upon their exposure to weathering.

Accurate forecasting of the short-term weathering reac-tions of the solids, which are the minerals in the wastes,and of the nature of the ensuing aqueous effluents is adifficult task because the tolerance range for the pH of effluents is rather narrow; once the pH decreases below that of rain (pH 5.6), biota and habitat can be negatively affected. Thus, for mining-related drainage, a pH of 5–5.5or lower generally marks the effluents as constituting acidrock drainage (ARD). In most mining jurisdictions today,a mine plan that includes the release of ARD to the envi-ronment is unlikely to obtain regulatory acceptance. Theresults of prediction tests of weathering, therefore, may beused to demonstrate an absence of potential ARD, or the

tests may be used to guide the development of plans thatcontrol or prevent the foreseen ARD. Such plans are acrucial facet of the mine-permitting process.Predictive techniques for potential ARD can be broadly grouped as kinetic tests and static tests. Both are similarinsofar as they are chemical tests independent of deter-minative mineralogy even though their purpose is topredict the weathering behavior of the minerals in thetested samples. A principal distinction between kinetic andstatic tests is the time factor. Kinetic tests utilize an ap-paratus, such as a column or cell, in which the sampledmaterial is periodically dosed with fluid or humidity, andthe leachates are analyzed to determine parameters such as

pH and the identity and quantity of ions that are solubi-lized over time. In contrast, a static test is a one-timemeasure that has the advantages of being rapid and rela-tively inexpensive. Most static tests involve two parts: (1)determination of the acid-producing potential, which isrelated to the amount of sulfide sulfur, assumed to bepresent in the sample as pyrite, and (2) determination of the amount of neutralization potential (NP), which is theamount of base released from the sample during a statictest. Only the latter part, that dealing with NP, is discussedhere.Although static tests have the advantages noted, thedisadvantage is that no information on reaction rates is

Received: 23 October 2001 / Accepted: 6 May 2002Published online: 21 June 2002ª Springer-Verlag (2002)

J.L. Jambor (&)Leslie Research and Consulting, 316 Rosehill Wynd,Tsawwassen, British Columbia, V4M 3L9 CanadaE-mail: [email protected].: +1-604-9481368Fax: +1-604-9481369

J.E. DutrizacCANMET, 555 Booth Street, Ottawa, K1A 0G1, Canada

J.L. Jambor Æ L.A. Groat Æ M. RaudseppDept. of Earth and Ocean Sciences,University of British Columbia, Vancouver,British Columbia V6T 1Z4, Canada

Original article

DOI 10.1007/s00254-002-0615-y Environmental Geology (2002) 43:1–17 1


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Table 1Localities and mineralogical character of the specimens

Mineral Simplified formulaa Locality b and commentsc

Olivine group

1. Forsterite, Fo93 (Mg,Fe)2SiO4 Light olive-green, polycrystalline; low-minor lizardite, traces phlogopite, talc,

chlorite, calcite; leached with acetic acidto remove calcite from the Sobek sample

2. Forsterite, Fo91 San Carlos, Arizona; gemstone quality,tumble-polished; trace serpentine

3. Fayalite, Fa89 (Fe,Mg,Mn)2SiO4 Forsythe Iron mine, Hull Township, Quebec;coarse-grained, intergrown with magnetite;Sobek sample shows trace magnetite

4. Fayalite Fa66 Vester Silfberg, Sweden; massive, withabundant phlogopite, amphibole, almandine

Pyroxene group5. Enstatite, En87 Mg2Si2O6 Amber, coarsely crystalline; trace amphibole6. Aegirine NaFe3+Si2O6 Summit mine, Marathon County,

Wisconsin; coarsely acicular7. Diopside, Wo49En34Fs17 Ca(Mg,Fe)Si2O6 Harcourt Township, Ontario; single

cleavage block; trace amphibole8. Diopside, Wo49En49Fs2 Almost white, coarse cleavage block;

trace tremolite, smectite, calcite9. Diopside, Wo50En43Fs7 Dark green, coarse cleavage block

Amphibole group10. Anthophyllite Mg7Si8O22(OH)2 Rakabedo mines, Udaipur, India;

fibrous aggregates to about 2 cm11. Grunerite Fe7Si8O22(OH)2 ‘‘Amosite’’, South Africa; fibrous,

asbestos-like; traces quartz, talc,biotite, hydrobiotite

12. Actinolite, Mg* =66 Ca2(Mg,Fe2+)5Si8O22(OH)2 Chester County, Pennsylvania; light green,

fibrous, polycrystalline; trace calciteconfirmed by reaction in acetic acid

13. Actinolite, Mg* =88 Light green, fibrous to 7 mm14. Actinolite, Mg* =88 Coarsely crystalline; low-minor chlorite15. Glaucophane Na2(Mg3Al2)Si8O22(OH)2 Mendocino County, California; schist-like;

low-minor mica, strong trace chlorite16. Ferropargasite NaCa2 Fe2þ4 Al

Si6Al2O22 OHð Þ2 Coarse cleavage fragment

17. Fluoro-edenite NaCa2Mg5Si7AlO22(F,OH)2 Wilberforce, Ontario; dark gray cleavagefragments

18. ‘‘Fluoro-ferro-eckermannite’’ NaNa2 Fe2þ4 Al

Si8O22 F; OHð Þ2 El Paso, Colorado; black, coarsely crystalline

19. ‘‘Sodicgrunerite’’ Na Fe2þ; Nað Þ2Fe2þ5 Si8O22 OHð Þ2 ‘‘Riebeckite’’, South Africa; blue, fibrous,

asbestos-like; trace quartz

Feldspar group20. Anorthite, An52 (Ca,Na)Al(Si,Al)3O8 ‘‘Labradorite’’, Newfoundland– Labrador;

coarsely crystalline; trace mica21. Anorthite, An65 Harp Lake, Newfoundland–Labrador;

coarsely crystalline; faint trace amphibole22. Anorthite, An67 ‘‘Bytownite’’, near Ottawa, Ontario;

coarsely crystalline

Mica group

23. Phlogopite KMg3AlSi8O10(OH)2 Single cleavage plate, 3·

4 cm24. Annite Katugin River, Siberia, Russia; black,platy to micaceous

Chlorite group25. Clinochlore, Mg* =84 (Mg, Fe2+)5Al(Si3Al)O10(OH)8 Clean, polycrystalline26. Clinochlore Mg* =62 Arctic Chief claim, Whitehorse, Yukon;

dark green, polycrystalline; trace mica,quartz, feldspar; strong trace epidote

27. Clinochlore Mg* =95 West Chester, Pennsylvania; medium green,single centimeters-wide plate

28. Clinochlore Mg* =62 Massive aggregate; clay reference series‘‘ripidolite’’ CMS-Cca-1; probably Flagstaff

Hill, El Dorado County, California;trace ilmenite

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Environmental Geology (2002) 43:1–17 3


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Table 1(Contd.)


29. Chamosite, Mg* =37 Hull, Quebec; fine-grained, massive, withplates of graphite; low-minor amphibole,trace biotite

Clay group

30. Halloysite Al2Si2O5(OH)4 Near Bedford, Indiana; American PetroleumInstitute (API) clay reference standard#12; fully and partly hydrated forms arepresent; kaolinite–serpentine group

31. Vermiculite–hydrobiotite K–Mg–Fe–Al silicates Montana, centimeters-wide coarse plates;mixed vermiculite–hydrobiotite, with thelatter predominant

32. Beidellite (Na,Ca0.5)0.3Al2(Si,Al)4O10(OH)2ÆnH2O Cameron, Arizona; API standard #31;smectite group; strong minor quartz,trace 7.3 Å mineral

33. Illite–smectite Composition K0:95Ca0:1Na0:09Mg0:03

Al3:39Fe3þ0:12Mg0:48

Si7:19Al0:81½ O20 OHð Þ4‘‘Czechoslovakia’’; Source Clays Repository,

University of Missouri, Columbia (UMC);standard ISCz-1, 70/30 ordered; strongtrace to low-minor quartz

34. Montmorillonite Composition Na0:32Ca0:12K0:05ð Þ Al3:01Fe

3þ0:41Mg0:54Ti0:02Mn0:01

Si7:98Al0:02½ O20 OHð Þ4Sodic montmorillonite; UMC standard,

presumably SWy-1, Crook County,

Wyoming; strong trace albite, tracescalcite, mica(?), quartz, feldspar(?);smectite group

35. Palygorskite Ca0:62Mg0:33K0:13Na0:04

Al1:50Fe

3þ0:52Mg1:91Ti0:06Fe

2þ0:01Mn0:01

Si7:88Al0:22½ O20 OHð Þ4Luten mine, Gadsden, Florida; UMC

standard PFl-1; strong trace quartz36. Saponite Ca1:14Na0:79K0:07ð Þ Mg5:98Mn0:01

Si7:19Al0:74Fe

3þ0:07

O20ðOHÞ4 Ballarat, California; UMC standard SapCa-2,

containing 3% diopside; smectite group

Garnet group37. Almandine, Alm71 (Fe

2+,Mg,Ca)3Al2(SiO4)3 Bella Vista mine, Mitkof Island, Alaska;four euhedral crystals totaling 5.6 g

38. Almandine, Alm49 Composite of subhedral to euhedral reddishgrains and crystals, each 2–3 mm across

39. Grossular, Gro96 (Ca,Mg)3Al2(SiO4)3 Parral, Chihuahua, Mexico; five euhedralcrystals, each 1–1.5 cm across

40. Almandine, Alm65 ‘‘Pyrope’’, Mt. McDonald, Queensland,Australia; composite of dark purplish

grains, each 2–3 mm acrossApatite group41. Fluorapatite Ca5(PO4)3(F,OH,Cl) St. Pierre de Wakefield, Quebec; coarse-

grained polycrystalline, bright light green42. Fluorapatite Dark green, coarsely polycrystalline43. Fluorapatite probably Durango, Mexico; large,

pale green single crystal44. Fluorapatite North Burgess, Ontario; blue, polycrystalline

Other minerals45. Epidote Ca2Al3(SiO4)3(OH) Dark green, coarse-grained46. Zoisite Ca2Al3(SiO4)3(OH) Franklin County, Mass.; light gray, coarse,

elongate cleavage fragments;minor chlorite, albite

47. Wollastonite CaSiO3 Whitehorse, Yukon; coarse-grained,massive; abundant celestine, trace quartz;

no fizz in HCl; the light fraction obtainedby separation in heavy liquids was tested

48. Wollastonite Calumet, Quebec; coarsely crystalline;leached with acetic acid to remove calcite

49. Pyrophyllite Al2Si4O10(OH)2 Tres Cerritos, Mariposa County, California;coarse divergent fibers

50. Clinochrysotile Mg3Si2O5(OH)4 Coarse cross fibers, 3.5 cm long; tracemagnetite

51. Magnetite Fe2 þ Fe3þ2 O4 Magnet Cove, Arkansas; massive

52. Goethite FeO(OH) Compact, coarsely crystalline, fibrousto 5 cm length

53. Hematite Fe2O3 Ironwood, Michigan; compact columnarto 15 cm length

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General results

Table 1 lists the mineral specimens that were examinedand gives the corresponding specific mineral species thatwere identified mainly on the basis of the X-ray data andthe microprobe compositions given in the Appendix. Clay minerals received as standards from recognized reposito-ries or authoritative sources were examined by X-ray dif-fractometry, but compositions and species identification

were accepted as provided.

Effect of associated carbonatesMost of the specimens selected for the study were of dis-play quality, but the data in Table 1 indicate that many contain small amounts of impurity minerals. Althoughmost of these impurities are of little concern because theireffects on the NP values are negligible, the presence of even minute amounts of carbonate minerals can lead tomisleading results that overestimate the potential NP of the host mineral. Even though all minerals in the study were examined by X-ray diffractometry prior to the NP

determinations, in some cases the presence of carbonate-mineral contamination was undetected or uncertain,mainly because of its low abundance, or because of dif-fraction-line overlap with the X-ray pattern of the hostmineral. The uncertainty was in some cases furthered by diffraction-line shifts and changes in intensity related tocompositional differences of the host mineral versus datapublished for diffraction-pattern standards. Thus, forseveral of the samples whose initially determined NP valuewas considered to be anomalously high, a new NP valuewas obtained after a split of the sample had been treatedwith diluted acetic acid to consume the suspected car-bonate. Nevertheless, because possible peripheral effects

on the host mineral as a consequence of the acetic acidleaching were not known, for all but two of the silicate-

mineral samples the initial NP tests were conducted withnon-leached material and on an assumed ‘‘no-fizz’’ basis.Table 2 compares the results for some of the samples thatwere regarded as having yielded anomalously high NPvalues, and for which subsequent testing showed reactionor possible reaction in acetic acid solution. For four of the acidified samples the surface areas were measuredbefore and after acid treatment. Surface areas of threeof the samples were higher after acidification, and that of

the fourth sample (actinolite) was slightly lower. Despitethe trend to increased surface areas, which shouldincrease NP as is noted below, all seven acid-treatedsamples have NP values that are substantially lower thanthe original ones.

Effect of particle size

Decreased particle size increases the surface area availablefor chemical reaction, thereby promoting reaction rates.Unless a mineral is totally consumed, it would be expectedthat the increased surface ‘‘availability’’ at finer particlesizes would lead to higher NP values. White and others

(1999) tested three rock samples, each at –325, –150,–60 mesh, and –1/4 inch (screen aperture 44, 106, 250 lm,and 6 mm, respectively), and observed a consistenttrend of increased NP as the particle size became finer.Figure 1 illustrates the effect of particle size versus NPvalues for three of the samples examined in our study. Foreach of the samples, the BET surface area increased as thescreened fraction became finer. The sole anomaly in thedeterminations was for the surface area of the minus 60-mesh fraction of anorthite, which yielded 0.200 m2/g.However, a split of that sample gave a surface area of 0.721 m2/g. Both samples gave similar NP values (11.5 and11.3 kg/t CaCO3 for the initial and split samples, respec-

tively). The higher surface area obtained from the splitsample, 0.721 m2/g, gives a normalized NP of 15.7 kg/t

Table 2NP values of selected samplesafter treatment with acetic acid.NP values in kg/t CaCO3. Min-eral numbers correspond to thelisting in Table 1

No., mineral Initial NP Surface area Effervescence Treated NP Sample SA(m2/g)

12. Actinolitea 79.5 1.643 Vigorous 1.5 1.5707. Diopside 17.8 0.279 Moderate 4.5 0.3888. Diopside 38.3 0.596 Vigorous 9.5 0.74317. Fluoro-edenite 29.8 0.228 Slight 1.7 –25. Clinochlore 14.3 – Trace 4.2 1.85841. Fluorapatite 28.3 0.086 Slight 2.7 –42. Fluorapatite 22.5 0.101 Slight 13.4 0.163

aFor the minus 325-mesh fraction because of insufficient original material at minus 60 mesh

Table 1(Contd.)


54. Jarosite KFe3(SO4)2(OH)6 Horn Silver mine, Utah; yellow, pulver-ulent

55. Jarosite Gold Hill mine, Utah; yellow, pulverulent

a

Specific compositions are given in the Appendix. Amphiboles 18 and 19 are new species not yet describedbUnless stated, the source locality is not knowncImpurities listed are based on SEM-EDS and X-ray diffractometry. Mg* = formula Mg/(Mg+Fe)·100

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CaCO3 equivalent, which is in accord with the values ob-tained from the finer fractions (Table 3). The remnants of the two samples, therefore, were re-screened to confirmtheir designated size, and as it was thought that the valueof 0.200 m2/g was anomalously low, the surface area of that sample was redetermined. The result, however, was0.197 m2/g, which is close to the original value (the tworesults are averaged as 0.199 m2/g in Table 3). The reasonfor the apparent discrepancy in the measured surface areasis not known.Table 3 shows that NP values consistently increase asparticle size becomes finer. The variation in NP fromsamples of –60 mesh to –325 mesh is less than 100% in all

cases, but the range is nevertheless significant with regardto sampling protocols and comparisons of the results fromdifferent NP test-methods. For example, the Lawrence (orBC. Modified) NP test stipulates that the sample be at 80%minus 200 mesh (75 lm); relative to the Sobek protocol,therefore, surface-area availability to reagent attack isgenerally higher if the Lawrence NP method is used.Table 3 shows also that the NP values normalized to unitsurface area decrease as the particle sizes become finer.Why this relationship exists is under further investigation,but the tentative explanation is that, even though the ex-tent of reaction of the solid is affected by the surface area,the two are not directly equivalent. Thus, in progressing

from –60 to –325 mesh, measured surface areas increasevariously by >3 to 7 times whereas the increase in NPvalues is


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parison with data for the forsterite sample from San Carlos(Table 1) and the previously tested forsterite, seems to betoo high, especially as all three specimens have an ex-tremely narrow compositional range (Fo 91–Fo 93). Thepossibility that some calcite was not removed by the acetic

acid leach was checked by grinding a portion of the acid-treated sample in a ceramic mortar and adding a few dropsof 1:1 HCl while observing the pulp under a binocularmicroscope. No indication of carbonate presence was de-tected.The NP values of the two fayalite samples are similar tothat of one of the forsterite samples. The high surface areafor one of the fayalite samples (Table 4) is the conse-quence of the multiple magnetic separations that wereused to eliminate the associated magnetite; the cleaningprocess resulted in the accumulation of the finer, non-intergrowth particles.

Pyroxene groupFour pyroxene samples were analyzed in the previousstudy and five were examined here. The results, summa-rized in Table 5, show that NP values range from 0.5 to 6.6,regardless of the surface area, and, therefore, are relatively low. The NP values normalized to unit surface area have aconsiderably greater range. Notable is that the two ensta-

tite samples of almost identical composition have similarly low NP values (3.2 and 6.3), but the normalized valuesdiffer considerably (2.1 and 41.7, respectively). The resultsin Table 5 do not demonstrate a specific correlation be-tween NP and the particular species of pyroxene that wastested; sample-to-sample variation seems to be as signifi-cant as any other factor.

Amphibole groupOnly two amphiboles were tested previously, but ten havebeen examined in this study. The compositions of theminerals are sufficiently diverse to provide an adequateassessment of the effect that solid–solution variations have

on the NP values of the minerals in the group.The results of the NP determinations are summarized inTable 6 and Fig. 2. The NP values are consistently low;nine of the samples have values


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Brantley (1995) observed that the dissolution rate forplagioclase follows a constant slope from An 0 to at leastAn 76, but under the conditions of the Sobek test thereseems to be an appreciable increase in NP and, therefore,in dissolution, at some point between An 52 and An 65(Fig. 3). The change is not broadly relatable to order–disorder phenomena (e.g., Stefánsson 2001), as samples onboth sides of the ’’break‘‘ are from plutonic-type ratherthan volcanic-type sources, and ordering should be grossly similar for the relevant feldspars.

Mica group

Three samples of mica were examined previously, and only two new samples were tested in this study. The previousstudy gave a low NP for muscovite, but higher values wereobtained for phlogopite (Table 8). The primary objectiveof the current study of mica was to test a high-Fe species,and this was accomplished by the acquisition of a speci-men of annite.The NP results for the five mica samples are summarizedin Table 8. All except one of the samples have low NP andlow normalized NP values. A split of the high-NP samplewas subsequently tested both with acetic acid solution andwith 1:4 HCl, but no bubbling indicative of carbonate-mineral presence was observed. The initial NP value was

29.5, and the NP determination for the sample treated withacetic acid gave 24.9. The lower value, which is given inTable 8, is still high, especially if it is noted that thecomposition of this specimen is bracketed by others thathave appreciably lower NP values. Microscopic examina-tion of a polished thin section of the untreated sample didnot reveal the presence of carbonates, and an infraredspectrum was likewise devoid of the absorption bandscharacteristic of CO3 groups.

To investigate further the possible cause of the high NPvalue, a second sample was cleaved from the same muse-um-quality specimen. The specimen is about 1 cm thick,and although it is not certain whether the cleaved face wasthe same as that used for the original sample, little dif-ference would be expected. Comminution and screeningwere done in the same way as for the initial test, but theresulting NP was much lower (Table 8). Thus, the reasonfor the higher NP of the original sample is not readily apparent.

Chlorite groupTwo samples of clinochlore were examined previously, andfive samples of chlorite were tested in this study (Table 9).The highest NP value was obtained for chamosite, but thissample also had the highest surface area, mainly becausethe fines were gradually concentrated as a consequence of attempts to purify the minus 60-mesh sample by separatingthe associated graphite. Addition of 1:1 HCl to asmall portion of the tested sample resulted in gradualdissolution, but no effervescence, and an infrared spectrumdid not reveal the presence of CO3 groups. Among the othersamples, all of which proved upon microprobe analysis tobe clinochlore, the highest NP value was 14.3. Redetermi-nation of this NP, after the sample had been treated withacetic acid solution, reduced the NP to 4.2 (Table 3).

Fig. 2NP values versus composition for the am-phiboles. Numbers for the tremolite–actino-lite series refer to formula Mg/(Mg+Fe)·100

Table 7NP values and surface areas of anorthite samples

Composition NP Surface area Normalized NP

An 50a 2.6 0.55 4.7An 52 5.3 0.629 8.4An 65 12.5 0.183 68.3An 67 11.5 0.199 57.8An 93a 10.7 0.75 14.3

a

Previous study (Jambor and others 2000a)

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The six clinochlore samples show considerable variation intheir NP values; however, the variation is within a limitedrange and is partly influenced by the large differences inthe surface areas of the tested samples (Table 9). Although

for clinochlore there may be a slight increase in NP as theMg contents increase, all of the chlorite samples, includingchamosite, have normalized NP values of


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Apatite groupThe focus on fluorapatite is unintended and is illustrativeof the difficulty in acquiring specimens that have a widerange of compositions in a particular solid–solution series.The four samples examined were originally labeled asapatite, chlorapatite, fluorapatite, and hydroxylapatite.Upon microprobe analysis, all proved to be fluorapatite,

albeit with a range of halogens and hydroxyl.Two of the four gave relatively high values of 22.5 and 28.3(Table 12). These two were leached with acetic acid solu-tion (Table 2), and the NP was subsequently redetermined.Although effervescence from both samples was classified

as slight, that of sample 40 was much the stronger, and theensuing reduction in NP was much greater than that forsample 41. Following the NP redeterminations, a portionof the remnant of sample 41, which still gave a moderateNP value of 13.4, was ground in a mortar and retested withacetic acid to ascertain whether possible occluded calcitehad been liberated by the reduction in grain size. The

number of bubbles that evolved suggests that traces of calcite were still present. Nevertheless, even if the presenceof carbonate-mineral contamination is totally discounted,the overall results from the various tests indicate that,unlike the carbonate minerals, the presence of accessory fluorapatite or chlorapatite will have a negligible influenceon the NP of the host rock. Although substitution of CO3for PO4 in the apatite series is known, the CO3-bearingminerals are generally not present in common rocks. Thetesting of hydroxylapatite, Ca5(PO4)3(OH), might be con-sidered to be of more practical relevance in terms of oc-currence and potential NP contribution; however,fluorapatite is reported by Deer and others (1966) to be by

far the most commonly occurring of the apatite-groupmembers. Moreover, even though the microprobe analysesindicate the maximum OH content of the tested mineralsto be only about 23 mol%, the NP of the sample richest inhydroxyl is notably low (Table 12).

Table 9NP values and surface areas of chlorite samples. Mg* [Mg/(Mg+Fe2+)]·100

Mineral Mg* NP Surface area Normalized NP

Clinochlorea 0.89 10.3 7.04 1.5Clinochlorea 0.61 0.8 1.50 0.525. Clinochloreb 0.84 4.2 1.86 2.3

26. Clinochlore 0.62 7.5 0.880 8.527. Clinochlore 0.95 12.5 2.968 4.228. Clinochlore 0.62 1.5 0.863 1.729. Chamosite 0.37 21.6 7.133 3.0

aPrevious study (Jambor and others 2000a)bAfter treatment with acetic acid solution; pre-treatment NP was 14.3

Table 10NP values and surface areas of clay-type samples

Mineral General formula/group NP Surface area Normalized NP

Kaolinitea Kaolinite–serpentine group, both Al2Si2O5(OH)4 0.0 17.1 0.0Halloysite 4.0 317 0.0Palygorskite (Mg,Al)2Si4O10(OH)Æ4H2O 21.1 106 0.2Hydrobiotite–vermiculite Interlayered K–Mg–Fe2+–Al silicates 29.0 4.87 6.0Illite–smectite Interlayered mica–smectite –2.7 24.0 –0.1Beidellite Smectite group 8.0 25.8 0.3Montmorillonitea Smectite group 13.8 31.4 0.4Montmorilloniteb Smectite group –2.5 19.4 –0.1Saponite Smectite group 37.5c 5.71 6.6

aPrevious study (Jambor and others 2000a)bAfter leaching with acetic acid; non-leached sample gave NP =25.0cCalcite presence detected by IR

Table 11NP values and surface areas of the garnets

Mineral Composition NP Surface area Normalized NP

Almandine (Fe2+,Mg,Mn,Ca)3Al2(SiO4)3 Alm 71 1.8 0.325 5.5Almandine Alm 65 1.3 0.080 16.3

Almandine Alm 49 5.3 0.054 98.1Grossular Ca3(Al,Fe

3+)2(SiO4)3 6.3 0.120 52.5

Table 12NP values and surface areas of the apatite-group minerals

Mineral General [and specific]composition

InitialNP

Surfacearea

FinalNPa

Surfacearea

NormalizedNP

40. Fluorapatite Ca5(PO4)3F;[F0.75(OH)0.23]

28.3 0.086 2.7 31.4

41. Fluorapatite [F0.59Cl0.40] 22.5 0.101 13.4b 0.163 82.2

42. Fluorapatite [F0.80Cl0.15] 8.0 0.088 90.943. Fluorapatite [F0.83(OH)0.16] 11.3 0.144 78.5

aNP after sample was treated with acetic acid solution. The surface area of sample 40 was not redeterminedbAdditional grinding and acidification suggests that traces of calcite are still present

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Other mineralsIn addition to the minerals already discussed, talc, antig-orite, and lizardite were previously tested. In the currentstudy, a test of epidote (clinozoisite) was considered to begermane because the mineral is a common accessory species and is locally a rock-forming mineral. Zoisite ismuch rarer, but is of relevance because it is the ortho-

rhombic polymorph of clinozoisite, which is monoclinic. Atest of clinochrysotile was pursued because, like antigoriteand lizardite, the mineral is a member of the kaolinite–serpentine group and, therefore, adds to the within-groupcomparisons. Results for the ’’other-mineral‘‘ category aresummarized in Table 13.Among the minerals in Table 13, two samples of wollas-tonite were tested. One had been treated with acetic acid toremove carbonate impurities, and as the possible effects of the treatment on the host mineral were unknown, theother sample was considered to provide an evaluationcontrol. Both samples, however, gave difficulties in the NPdetermination, and it was found necessary to increase

progressively the acidity levels (Table 13). The resultingNP values are extremely high, approaching those of thecarbonate minerals.If it is assumed that the hydrolysis of wollastonite(Rimstidt and Dove 1986) is represented by

CaSiO3þ2HþþH2O ! Ca

2þþH4SiO4 ð1Þ

then the neutralization potential is equivalent to that of calcite, as represented by the reaction

CaCO3þ2Hþ ! Ca2þþCO2þH2O ð2Þ

In both reactions, 1 mol of the mineral consumes 2 H+.However, the higher molar weight of wollastonite relative

to that of calcite results in a theoretical NP of 861 forwollastonite. The measured values obtained in the tests arelower (Table 13) and are taken to be an indication that thewollastonite was not fully consumed.Other minerals tested were magnetite, hematite, goethite,and jarosite, all of which gave low NP values (Table 13).Although these minerals were not analyzed by microprobe,X-ray diffractograms and wet-chemical analyses of the

jarosite samples indicate that the material from the GoldHill mine is a mixture of natrojarosite and jarosite; theanalysis of jarosite from the Horn Silver mine gave K2O9.80, Na2O 0.09, PbO 0.64, Fe2O3 44.26, Al2O3 0.01, SO329.49, sum 84.29 wt%, corresponding to (K1.13Na0.02Pb0.03)S1.18Fe3.01(SO4)2(OH)6.21.

Discussion

In the static-test prediction of potential ARD, recourse iscommonly made to the ratio of acid-producing potential(AP) versus NP rather than to the absolute value of the NP.For a rock to be deemed as not acid-generating, the des-ignated value of NP:AP varies in different jurisdictions; forexample, it is 3:1 in California and 1.2:1 in Nevada(Lawrence and Wang 1996). Prior to the adoption of theapproach to using NP:AP ratios in British Columbia, only material with an NP value of more than 20 kg CaCO3equivalent was categorized as ‘‘not acid-producing’’

(Errington 1991). Materials giving NP values of 20 to –20were classified ‘‘uncertain’’ as to whether they wouldgenerate ARD or be environmentally benign. An NP valueof 20, therefore, is a convenient reference level for evalu-ating the NP values that have been obtained for the variousminerals. A relevant point is that, to consume 20 units of NP, a rock sample would have to contain 0.64 wt% S aspyrite, which is equivalent to about 1.2 wt% pyrite.The 55 mineral specimens investigated in this study, to-gether with the data reported by Jambor and others(2000a) for 28 additional samples, provide a useful basisfor assessing the potential sources of NP in mine-relatedwastes. Except for olivine, carbonates, and wollastonite,

and perhaps serpentine, it is evident that most rock-forming minerals will yield insufficient base to meet arequirement that the NP be ‡20. For rocks not containingolivine–serpentine or wollastonite, which means the vastmajority of common rock types, even ’’barren‘‘ samples(those completely devoid of sulfide minerals) would fallinto the ’’uncertain‘‘ rather than the ’’not acid-generating‘‘category unless the rock contained at least small amounts

Table 13NP values and surface areas of miscellaneous minerals

Mineral General formula NP Surface area Normalized NP

Talca Mg3Si4O10(OH)2 1.7 3.04 0.6Antigoritea (Mg,Fe2+)3Si2O5(OH)4 15.1 39.3 0.4Lizarditea Mg3Si2O5(OH)4 16.1 2.05 7.9

Clinochrysotileb Mg3Si2O5(OH)4 87.6 40.43 2.2Wollastonitec CaSiO3 440 0.199 2211Wollastonitec,d 567 17.09 33.2Epidote Ca2Al3(SiO4)3(OH) 1.0 0.069 14.5Zoisite Ca2Al3(SiO4)3(OH) 3.0 0.058 51.7Pyrophyllite Al2Si4O10(OH)2 0.3 7.57 0.0Magnetite Fe2þFe3þ2 O4 1.7 0.560 3.0Goethite FeO(OH) 1.5 5.353 0.3Hematite Fe2O3 2.0 3.013 0.7Jarosite KFe3(SO4)2(OH)6 –3.9 1.785 –2.2Jarosite 2.9 1.985 1.5

aPrevious study (Jambor and others 2000a)bTested with 40 ml of 0.1 N HClcTested with 80 ml of 0.5 N HCldLeached with acetic acid solution to remove calcite

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of a carbonate mineral. For example, granite, a rock typ-ically consisting largely of quartz, K-feldspar, and sodicplagioclase, together with small amounts of mica or am-phibole, would typically have an NP of 5 or less. Similarly,the complete spectrum of common plutonic rocks, rangingfrom granite to syenite, diorite, gabbro, and anorthosite, aswell as their effusive and sedimentary and metamorphic

counterparts, would yield NP values of 20) NP values; for other silicate, alumi-nosilicate, and phosphate minerals, several of the highestNP values were traceable to contamination by smallamounts of carbonate minerals.Other than for highly calcic feldspar, compositional vari-ations and polymorphism within a mineral group do notseem to have profound effects on NP. In the amphibole

group, for example, the total range of experimental NPvalues is 0.2–8.7, and at least part of that range is attrib-utable to the appreciably different surface areas of thetested samples. The indication from Table 6 is that thecommon rock-forming amphiboles will give an NP of nomore than 5 units. For the feldspar group, sodic andpotassic members yield little NP, and even Ca-bearing

members give little NP until compositions are well into thefield of anorthite (Table 7). In laboratory dissolution ex-periments at pH 3, Stillings and Brantley (1995) observed astraight-line increase in dissolution rates in the albite–anorthite series to at least An 76. In the conditions of theNP tests, however, NP values were found to increase from5.3 at An 52, to >10 at An ‡65.Reductions in particle sizes lead to an increased NP, but a100% increase in surface area only increases the NP by 1 to


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Pyroxene group. The numbers in the column heads refer to: 5

Mg1:74Fe2þ0:13Ca0:02Mn0:01Cr0:01Fe

3þ0:05

R2:00

Si1:94Al0:05Fe3þ0:01

R2:00

O6; 6 Na0:96Fe2þ0:08Fe

3þ0:91Al0:04Ti0:01

R2:00

Si2:00O6; 7

Ca0:95Na0:04Mg0:66Fe2þ0:25Mn0:01Fe

3þ0:08

R1:99

Si1:96Al0:05ð ÞR2:01O6; 8

Ca0:98Na0:03Mg0:86Fe2þ0:13Mn0:01

R2:00

Si1:98Al0:03ð ÞR2:01O5:99F0:01

Specimen 5, n=5; enstatite 6, n=5; aegirine 7, n=5; diopside 8, n=5; diopside

wt% Na2O 0.00 12.68 (12.28–12.84) 0.59 (0.56–0.63) 0.37 (0.36–0.39)CaO 0.40 (0.24–0.83) 0.08 (0.01–0.13 23.34 (23.23–23.47) 0.01 (0.00–0.02)MgO 33.53 (33.22–33.76) 0.06 (0.02–0.16) 11.63 (11.45–11.80) 24.80 (24.65–24.88)MnO 0.18 (0.14–0.22) 0.05 (0.00–0.11) 0.25 (0.21–0.30) 15.66 (15.62–15.75)FeO 6.30 (5.48–6.76) 2.68 (1.79–2.74) 7.91 (7.14–8.57) 0.18 (0.17–0.20)Al2O3 55.83 (55.24–55.95) 0.77 (0.20–1.26) 1.01 (0.98–1.06) 4.05 (3.93–4.26)Fe2O3 2.22 (1.93–3.05) 31.09 (29.13–33.27) 2.92 (2.63–3.45) 0.79 (0.74–0.85)Cr2O3 0.44 (0.41–0.50) 0.00 0.05 (0.03–0.07) 0.00 (0.00–0.03)TiO2 0.02 (0.00–0.05) 0.25 (0.05–0.45) 0.03 (0.02–0.04) 0.02 (0.00–0.04)SiO2 55.83 (55.24–55.95) 51.43 (50.98–51.86) 51.43 (51.05–51.78) 53.48 (53.28–53.95)Cl 0.01 (0.00–0.02)F 0.06 (0.04–0.07)O ” F –0.03 (0.02–0.03)Total 100.06 (99.57–100.75) 99.09 (98.37–99.42) 99.16 (98.80–99.52) 99.40 (99.16–99.60)

Pyroxene group. The number in the column head refer to: 9 Ca0:99Na0:01Mg0:96Fe2þ0:04

R2:00 Si1:99Al0:02ð ÞR2:01O6

Specimen 9, n=5; diopside

wt% Na2O 0.18 (0.09–0.25)K2O 0.00CaO 25.37 (25.20–25.55)MgO 17.73 (17.36–17.95)MnO 0.13 (0.09–0.17)FeO 1.16 (1.00–1.36)Al2O3 0.55 (0.20–0.88)Cr2O3 0.01 (0.00–0.02)TiO2 0.01 (0.00–0.04)SiO2 54.70 (54.61–54.78)Total 99.84 (99.67–100.00)

Amphibole group. The numbers in the column heads refer to: 10Mg5:00 Mg0:87Fe1:03Mn0:03Ca0:06Na0:01

R2:00

Si7:99Al0:01ð ÞR8:00O22:99F0:01; 11

K0:01 Mg1:49Fe2þ0:46Ca0:02Na0:01

R1:98

Fe2þ4:49Mn0:49Al0:02

R5:00Si8:01O22:98Cl0:02; 12

Ca0:03Na0:04K0:01 Ca1:94Fe0:03Mn0:03ð ÞR2:00 Mg3:28Fe2þ1:69Al0:03

R5:00

Si7:80Al0:20ð ÞO22:95F0:03Cl0:02

Specimen 10, n=5; anthophyllite 11, n=1; grunerite 12, n=5; actinolite

wt% Na2O 0.03 (0.01–0.05) 0.03 0.15 (0.10–0.20)K2O 0.00 (0.00–0.01) 0.05 0.07 (0.06–0.10)CaO 0.42 (0.38–0.44) 0.09 12.55 (12.43–12.71)MgO 28.83 (28.71–29.02) 6.13 15.04 (14.57–16.08)MnO 0.23 (0.19–0.30) 3.54 0.27 (0.24–0.32)

FeO 8.98 (8.70–9.12) 36.39 14.08 (12.66–14.48)Al2O3 0.07 (0.06–0.10) 0.09 1.35 (0.66–2.05)Cr2O3 0.03 (0.00–0.06) 0.02 0.00TiO2 0.01 (0.00–0.02) 0.01 0.01 (0.00–0.01)SiO2 58.45 (57.97–58.96) 49.29 53.32 (52.49–54.45)Cl 0.00 0.06 0.06 (0.03–0.09)F 0.02 (0.00–0.05) 0.00 0.06 (0.05–0.10)O ” Cl –0.01 –0.02 (0.01–0.02)O ” F –0.01 –0.03 (0.02–0.04)Total 97.06 (96.16–97.79) 95.69 96.91 (96.23–97.57)

Amphibole group. The numbers in the column heads refer to: 13Na0:03 Ca1:93Mg0:06Na0:01

R2:00

Mg4:35Fe2þ0:58Mn0:03Cr0:01Al0:03

R5:00

Si7:87Al0:13ð ÞO22:98F0:01; 14

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Na0:04 Ca1:84Fe0:12Mn0:03Na0:01ð ÞR2:00 Mg4:48Fe2þ0:48Al0:03Cr0:01

R5:00

Si7:94Al0:06ð ÞR8:00O22 OHð Þ2; 15

Na0:06 Na1:69Ca0:17Mg0:14

R2:00 Mg1:70Al1:69Fe

2þ1:60Mn0:01

R5:00

Si7:92Al0:08ð ÞO23; 16

Na0:58K0:37ð ÞR0:95 Ca1:83Mn0:15Na0:02ð ÞR2:00 Fe2þ3:20Mg1:42Al0:29Ti0:06Mn0:03

R5:00

Si6:19Al1:81ð ÞO22:52F0:42Cl0:06

Specimen 13, n

=5; actinolite 14, n

=5; actinolite 15, n

=5; glaucophane 16, n

=4; ferropargasitewt% Na2O 0.13 (0.07–0.21) 0.18 (0.12–0.26) 6.45 (5.68–6.77) 1.97 (1.88–2.03)

K2O 0.02 (0.01–0.03) 0.02 (0.00–0.04) 0.02 (0.01–0.03) 1.82 (1.76–1.86)CaO 12.86 (12.64–13.05) 12.38 (12.24–12.59) 1.12 (0.32–2.60) 10.80 (10.64–10.93)MgO 21.09 (20.45–21.49) 21.64 (21.18–21.95) 8.80 (7.57–9.20) 6.02 (5.95–6.10)MnO 0.26 (0.22–0.31) 0.23 (0.17–0.27) 0.11 (0.04–0.19) 1.36 (1.28–1.44)FeO 4.95 (4.67–5.27) 5.13 (4.51–5.64) 13.64 (12.59–16.70) 24.25 (24.14–24.42)Al2O3 0.99 (0.48–1.89) 0.56 (0.16–0.82) 10.71 (9.11–11.75) 11.31 (11.05–11.56)Cr2O3 0.13 (0.06–0.23) 0.10 (0.06–0.15) 0.01 (0.00–0.02) 0.00 (0.00–0.02)TiO2 0.02 (0.00–0.05) 0.01 (0.00–0.03) 0.03 (0.01–0.05) 0.50 (0.47–0.51)SiO2 56.18 (55.24–57.15) 57.15 (56.91–57.47) 56.49 (55.27–57.56) 39.22 (38.88–39.48)Cl 0.02 (0.00–0.05) 0.00 0.01 (0.00–0.02) 0.22 (0.14–0.33)F 0.03 (0.00–0.07) 0.00 0.00 (0.00–0.01) 0.84 (0.80–0.86)O ” Cl –0.05 (0.03–0.07)O ” F –0.01 (0.00–0.03) –0.35 (0.34–0.36)Total 96.67 (95.75–97.11) 99.56 (99.18–99.88) 97.39 (96.59–97.98) 97.91 (97.83–97.97)

Amphibole group (continued). The numbers in the column heads refer to: 17

Na0:78 Ca1:32Na0:41K0:27ð ÞR2:00 Mg4:64Fe2þ0:26Mn0:02

R4:92

Si7:46Al0:32Ti0:04ð ÞR7:82O21:90F1:09Cl0:01; 18

Na0:70K0:36ð Þ Na1:99Ca0:01ð Þ Fe2þ4:01Mn0:17Ti0:14Al0:12Mg0:01

R4:45

Si8:08O21:72F1:28; 19

Na0:82K0:02ð Þ Mg0:83Na0:82Fe2þ0:26Ca0:07Mn0:02

R2:00

Fe2þ5 Si7:96Al0:01ð ÞR7:97O22:97Cl0:03

Specimen 17, n=5; fluoro-edenite 18, n=5; ’’fluoro-ferro-eckermannite‘‘ 19, n=1; ’’sodicgrunerite‘‘

wt% Na2O 4.49 (4.39–4.74) 8.69 (8.60–8.82) 5.37K2O 1.52 (1.30–1.62) 1.75 (1.62–1.96) 0.09CaO 8.94 (8.68–9.36) 0.03 (0.02–0.05) 0.40

MgO 22.69 (22.59–22.86) 0.06 (0.04–0.07) 3.34MnO 0.17 (0.13–0.21) 1.22 (1.17–1.32) 0.16FeO 2.30 (2.03–2.50) 30.03 (29.60–30.69) 37.52Al2O3 1.97 (1.34–2.19) 0.64 (0.56–0.68) 0.03Cr2O3 0.01 (0.00–0.04) 0.01 (0.00–0.04) 0.01TiO2 0.37 (0.30–0.45) 1.20 (1.12–1.32) 0.00SiO2 54.35 (53.62–55.12) 50.58 (50.26–50.84) 47.50Cl 0.02 (0.00–0.03) 0.01 (0.00–0.02) 0.09F 2.52 (2.40–2.60) 2.53 (2.45–2.61) 0.00O ” Cl –0.01 (0.00–0.01) 0.00 –0.02O ” F –1.06 (1.01–1.09) –1.07 (1.03–1.10) 0.00Total 98.28 (97.79–98.77) 95.68 (95.53–96.10) 94.49

Feldspar group. The numbers in the column heads refer to: 20 Ca0:52Na0:46K0:01ð ÞR0:99Al1:50Si2:49O8; 21

Ca0:

65Na0:

33K0:

01ð ÞR0:99Al1

:

63Fe0:

01Si2:

36O8; 22

Ca0:

67Na0:

33K0:

01Mg0:01

R0:99Al1

:

62Fe0:

03Si2:

35O8

Specimen 20, n=5; anorthite 21, n=5; anorthite 22, n=5; anorthite

wt% Na2O 5.31 (5.08–5.43) 3.70 (3.24–4.10) 3.42 (3.10–3.49)K2O 0.21 (0.15–0.26) 0.26 (0.19–0.30) 0.19 (0.14–0.23)CaO 10.72 (10.52–10.98) 13.32 (12.71–14.36) 13.81 (13.05–14.30)MgO 0.00 (0.00–0.01) 0.01 (0.00–0.02) 0.09 (0.08–0.10)Al2O3 28.26 (28.07–28.68) 30.46 (29.89–31.25) 30.08 (29.22–30.53)Fe2O3 0.14 (0.09–0.18) 0.31 (0.28–0.38) 0.77 (0.69–0.83)SiO2 55.39 (55.08–55.69) 52.19 (51.14–53.01) 51.53 (50.53–52.71)Total 100.03 (99.74–100.25) 100.25 (99.60–100.67) 99.89 (99.38–100.13)

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Mica group. The numbers in the column heads refer to: 23

K0:88Na0:10ð ÞR0:98 Mg2:22Fe2þ0:60Ti0:08Al0:04Mn0:01

R2:95

Si2:95Al1:05ð ÞR4:00O10 OH1:87F0:12ð Þ; 24

K0:95Na0:03ð ÞR0:98 Fe2þ2:47Ti0:20Mn0:07Mg0:05

R2:79

Si3:16Al0:79ð ÞR3:95O10 OH1:01F0:97Cl0:02ð Þ

Specimen 23, n=5; phlogopite 24, n=5; annite

wt% Na2O 0.68 (0.63–0.70) 0.17 (0.06–0.03)K2O 9.44 (9.23–9.61) 8.80 (8.47–8.95)MgO 20.37 (20.29–20.47) 0.39 (0.35–0.41)MnO 0.21 (0.15–0.30) 0.92 (0.80–1.01)FeO 9.72 (9.49–9.86) 34.81 (33.07–35.75)BaO 0.16 (0.04–0.24) 0.02 (0.00–0.05)Al2O3 12.62 (12.51–12.71) 7.87 (7.71–8.23)Cr2O3 0.02 (0.00–0.08) 0.01 (0.00–0.03)TiO2 1.39 (1.32–1.46) 3.18 (2.90–3.43)SiO2 40.31 (39.91–40.61) 37.21 (36.89–37.62)Cl 0.03 (0.00–0.08) 0.12 (0.10–0.14)F 0.53 (0.49–0.57) 3.62 (3.39–3.73)[H2O] 3.84 (3.83–3.85) 1.78 (1.68–1.92)O ” Fl 0.01 (0.00–0.02) 0.03 (0.02–0.03)O ” Cl 0.22 (0.21–0.24) 1.52 (1.43–1.57)Total 99.09 (98.57–99.58) 97.35 (95.27–98.15)

Chlorite group. The numbers in the column heads refer to: 25

Mg4:16Fe2þ0:77Mn0:01Cr0rm:01

R4:95

Si3:09Al1:91ð ÞR5:00O10 OHð Þ8; 26

Mg2:88Fe2þ1:80Al0:24Mn0:03Cr0:01Ti0:01

R4:97

Si2:79Al2:21ð ÞR5:00O10ðOHÞ8; 27

Mg4:61Fe2þ0:26Cr0:09

R4:96

Si2:99Al2:00ð ÞR4:99O10ðOHÞ8; 28 Mg2:94Fe2þ1:83Al0:21Mn0:01Ti0:01

R5:00

Si2:77Al2:23ð ÞR5:00O10ðOHÞ8; 29

Fe2þ3:18Mg1:83Mn0:02Ti0:01

R5:04 Si3:38Al1:47ð ÞR4:85O10ðOHÞ8

Specimen 25, n=5 clinochlore 26, n=3; clinochlore 27, n=5; clinochlore 28, n=5; clinochlore 29, n=5; chamosite

wt% MgO 28.42 (27.34–29.37) 18.47 (18.04–18.81) 32.34 (32.16–32.52) 18.91 (18.76–19.07) 11.04 (10.16–12.90)MnO 0.11 (0.07–0.18) 0.30 (0.28–0.33) 0.02 (0.00–0.05) 0.08 (0.04–0.13) 0.22 (0.16–0.29)FeO 9.33 (8.27–10.26) 20.64 (20.40–20.98) 3.25 (3.13–3.41) 20.95 (20.29–21.41) 34.14 (31.33–35.69)Al2O3 16.48 (15.52–17.81) 19.91 (19.53–20.41) 17.77 (17.43–17.96) 19.90 (19.59–20.20) 11.20 (11.02–11.29)Cr2O3 0.17 (0.06–0.48) 0.14 (0.07–0.20) 1.25 (1.10–1.37) 0.05 (0.00–0.10) 0.01 (0.00–0.02)

TiO2 0.02 (0.00–0.03) 0.10 (0.07–0.14) 0.03 (0.00–0.05) 0.08 (0.06–0.11) 0.07 (0.00–0.21)SiO2 31.46 (30.70–32.03) 26.76 (26.52–26.99) 31.23 (31.04–31.41) 26.57 (26.02–26.97) 30.37 (29.70–31.02)[H2O] 12.21 (12.17–12.26) 11.48 (11.43–11.52) 12.54 (12.47–12.59) 11.51 (11.33–11.64) 10.78 (10.66–10.90)Total 98.20 (97.88–98.70) 97.87 (97.34–98.12) 98.43 (97.86–98.90) 98.05 (96.38–99.33) 97.83 (97.46–98.57)

Garnet group. The numbers in the column heads refer to: 37

Fe2:10Mg0:54Mn0:21Ca0:10K0:01

R2:96 Al2:02Fe

3þ0:05

R2:07

SiO4ð Þ2:96; 38 Fe1:48Mg1:15Ca0:34Mn0:04

R3:01Al2:02Si2:98O12; 39

Ca2:98Mg0:10Mn0:01

R3:09 Al1:80Fe

3þ0:18Ti0:02

Si2:96O12; 40 Fe1:92Mg0:89Ca0:10Mn0:06

R2:97

Al2:05Si2:97O12

Specimen 37, n=5; almandine 38, n=5; almandine 39, n=5; grossular 40, n=5; almandine

wt% Na2O 0.03 (0.02–0.05) 0.02 (0.01–0.03) 0.00 (0.00–0.01) 0.01 (0.01–0.02)MgO 4.56 (4.25–4.77) 9.95 (9.73–10.20) 0.84 (0.74–0.90) 7.11 (6.11–8.14)MnO 3.12 (20.8–4.81) 0.66 (0.59–0.71) 0.17 (0.14–0.18) 1.53 (0.89–2.57)FeO 31.41 30.22–32.33) 23.68 (23.21–23.95) 29.52 (28.63–30.95)Al2O3 21.48 (21.36–21.70) 22.55 (22.44–22.66) 20.13 (19.68–20.65) 22.30 (22.03–22.49)Fe2O3 0.82 (0.55–1.31) 3.17 (2.92–3.50)Cr2O3 0.03 (0.00–0.05) 0.02 (0.00–0.06) 0.02 (0.00–0.06) 0.01 (0.00–0.03)TiO2 0.06 (0.02–0.12) 0.06 (0.02–0.07) 0.33 (0.18–0.45) 0.01 (0.00–0.02)SiO2 37.06 (36.99–37.13) 39.00 (38.86–39.09) 39.08 (38.92–39.24) 38.03 (37.72–38.30)Total 99.79 (99.53–100.07) 100.05 (99.70–100.27) 100.48 (99.84–100.36) 99.97 (99.40–100.35)

Apatite group. The numbers in the column heads refer to: 41

Ca5:10Sr0:01ð ÞR5:11 PO4ð Þ2:95 SiO4ð Þ0:01 F0:75 OHð Þ0:23Cl0:02

R1:00; 42

Ca5:08Sr0:01ð ÞR5:09 PO4ð Þ2:93 SiO4ð Þ0:04 F0:59Cl0:40 OHð Þ0:03

R1:02; 43

Ca5:02Ce0:02La0:01ð ÞR5:05 PO4ð Þ2:96 SiO4ð Þ0:02 F0:80Cl0:15 OHð Þ0:05

R1:00; 44 Ca4:91Mn0:16ð ÞR5:07 PO4ð Þ2:97 F0:83 OHð Þ0:16

R0:99

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Specimen 41, n=5; fluorapatite 42, n=5; fluorapatite 43, n=5; fluorapatite 44, n=5; fluorapatite

wt% Na2O 0.00CaO 55.42 (55.32–55.49) 54.97 (54.82–55.16) 54.52 (54.37–54.83) 53.69 (53.42–54.96)SrO 0.28 (0.26–0.33) 0.21 (0.17–0.30)MgO 0.00MnO 0.00 0.00 0.00 2.21 (2.06–2.35)FeO 0.00

Al2O3 0.00Cr2O3 0.00La2O3 0.41 (0.24–0.51) 0.00Ce2O3 0.57 (0.43–0.68) 0.00TiO2 0.00SiO2 0.17 (0.15–0.18) 0.41 (0.37–0.44) 0.23 (0.20–0.26) 0.00P2O5 40.53 (39.97–40.92) 40.16 (39.85–40.83) 40.63 (40.49–40.81) 41.16 (40.73–41.39)Cl 0.15 (0.09–0.20) 2.75 (2.42–2.92) 1.05 (0.94–1.17) 0.02 (0.00–0.10)F 2.76 (2.67–2.85) 2.15 (2.07–2.24) 2.95 (2.89–3.05) 3.09 (2.99–3.17)[H2O] 0.40 (0.37–0.47) 0.06 (0.02–0.09) 0.08 (0.01–0.12) 0.29 (0.26–0.34)O ” Cl 0.04 (0.02–0.05) 0.62 (0.55–0.67) 0.23 (0.21–0.26) 0.00 (0.00–0.02)O ” F 1.16 (1.12–1.20) 0.90 (0.87–0.94) 1.24 (1.22–1.28) 1.30 (1.26–1.33)Total 98.51 (98.06–98.89) 99.19 (98.77–99.78) 98.97 (98.77–99.47) 99.16 (98.57–99.51)

Other minerals. The numbers in the column heads refer to: 45 Ca2:01 Al2:89Fe3þ0:10

R2:99

SiO4ð Þ2:99 OHð Þ; 46

Ca2:01 Al2:23Fe3þ0:76Ti0:01

R3:00 SiO4ð Þ2:99 OHð Þ; 47 Ca1:99Fe0:01ð ÞR2:00Si2:00O6

Specimen 45, n=5; clinozoisite 46, n=5; zoisite 47, n=4 wollastonite

wt% Na2O 0.01 (0.00–0.02) 0.01 (0.00–0.04) 0.01 (0.00–0.02)CaO 24.66 (24.47–24.90) 23.76 (23.48–24.01) 48.02 (47.78–48.42)MgO 0.03 (0.01–0.03) 0.03 (0.02–0.03) 0.03 (0.01–0.05)MnO 0.08 (0.03–0.12)FeO 0.38 (0.29–0.45)BaO 0.03 (0.00–0.06)Al2O3 32.26 (31.97–32.55) 23.92 (23.21–25.17) 0.01 (0.00–0.02)Mn2O3 0.03 (0.02–0.05) 0.07 (0.04–0.13)Fe2O3 1.77 (1.49–2.22) 12.74 (11.19–13.80)Cr2O3 0.01 (0.00–0.05) 0.01 (0.00–0.04) 0.01 (0.00–0.02)TiO2 0.08 (0.03–0.18) 0.16 (0.06–0.28) 0.01 (0.00–0.03)SiO2 39.29 (39.16–39.63) 37.81 (37.54–38.13) 51.73 (51.48–51.89)

[H2O] 1.97 (1.96–1.98) 1.90 (1.89–1.91)Total 100.11 (99.66–100.53) 100.41 (100.13–100.61) 100.31 (99.80–100.63)

Other minerals (continued). The numbers in the column heads refer to: 48 Ca1:98Fe0:02ð ÞR2:00Si2:00O6; 49Na0:01Al1:95Si4:03O10 OHð Þ2; 50 Mg2:74Fe0:13

R2:87

Si2:06O5 OHð Þ4

Specimen 48, n=5 wollastonite 49, n=5 pyrophyllite 50, n=2;clinochrysotile

wt% Na2O 0.00 (0.00–0.02) 0.07 (0.03–0.11) 0.00CaO 47.82 (47.15–48.07) 0.00 0.00MgO 0.06 (0.01–0.21) 0.00 39.96 (39.71–40.21)MnO 0.07 (0.04–0.11) 0.00 0.06 (0.05–0.07)FeO 0.58 (0.40–0.91) 0.09 (0.04–0.14) 3.51 (3.26–3.75)NiO 0.04 (0.00–0.08)

BaO 0.05 (0.00–0.14)Al2O3 0.00 (0.00–0.01) 26.80 (26.45–27.51) 0.02 (0.01–0.03)Cr2O3 0.00 (0.00–0.01) 0.00 0.01 (0.00–0.01)TiO2 0.02 (0.00–0.03) 0.00 0.00SiO2 51.61 (51.28–51.97) 65.33 (64.19–66.54) 44.82 (44.80–44.84)[H2O] 4.86 (4.78–4.96) 13.04 (13.02–13.06)Total 100.21 (99.79–100.61) 97.15 (95.68–99.12) 101.47 (101.38–101.53)

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References

Chipera SJ, Bish DL (2001) Baseline studies of the Clay MineralsSociety source clays: powder X-ray diffraction analysis. ClaysClay Minerals 49:398–409

Deer WA, Howie RA, Zussman J (1966) An introduction to therock-forming minerals. Longman, London

Errington JC (1991) The regulation of acid mine drainage. Pro-ceedings Second International Conference on Abatement of Acidic Drainage, vol 2. MEND, Natural Resources Canada,Ottawa, pp 89–99

Jambor JL (2000) The relationship of mineralogy to acid- andneutralization-potential values in ARD. In: Campbell LS, Vals-ami-Jones E, Batchelder M (eds) Environmental mineralogy:microbial interactions, anthropogenic influences, contaminatedland and waste management. Mineral Soc Lond, Mineral Soc Ser9:141–159

Jambor JL, Blowes DW (1998) Theory and applications of min-eralogy in environmental studies of sulfide-bearing mine wastes.In: Cabri LJ, Vaughan DJ (eds) Modern approaches to ore andenvironmental mineralogy, vol 27. Mineralogical Association of Canada, Nepean, Ontario. Short-course, pp 367–401

Jambor JL, Dutrizac JE, Chen TT (2000a) Contribution of specificminerals to the neutralization potential in static tests. Fifth In-ternational Conference on Acid Rock Drainage, vol 1. SME,Denver, pp 551–565

Jambor JL, Blowes DW, Ptacek CJ (2000b) Mineralogy of minewastes and strategies for remediation. In: Vaughan DJ,

Wogelius RA (eds) Environmental mineralogy. EMU NotesMineral 2:255–290

Lawrence RW, Wang Y (1996) Determination of neutralizationpotential for acid rock drainage prediction. Natural ResourcesCanada, Ottawa. Draft Report, MEND Project 1.16.3

Mermut AR, Faz Cano A (2001) Baseline studies of the Clay Minerals Society source clays: chemical analyses of major ele-ments. Clays Clay Minerals 49:381–386

Rimstidt JD, Dove PM (1986) Mineral/solution reaction rates in amixed flow reactor: wollastonite hydrolysis. Geochim Cosmo-chim Acta 50:2509–2516

Sobek AA, Schuller WA, Freeman JR, Smith RM (1978) Field andlaboratory methods applicable to overburdens and minesoils.US Environmental Protection Agency Report EP-600/2-78-054

Stefánsson A (2001) Dissolution of primary minerals of basalt innatural waters I. Calculation of mineral solubilities from 0C to350C. Chem Geol 172:225–250

Stillings LL, Brantley SL (1995) Feldspar dissolution at 25C andpH 3: reaction stoichiometry and the effect of cations. GeochimCosmochim Acta 59:1483–1496

White AF, Brantley JL (eds) (1995) Chemical weathering rates of silicate minerals. Mineral Soc Am, Rev Mineral vol 31

White WW III, Lapakko KA, Cox RL (1999) Static-test methods

most commonly used to predict acid-mine drainage: practicalguidelines for use and interpretation. In: Plumlee GS, LogsdonMJ (eds) The environmental geochemistry of mineral deposits,part A: processes, techniques, and health issues. Rev Econ Geol6A:325–338

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Static Tests of Neutralization Potentials of Silicate