Upload
others
View
0
Download
0
Embed Size (px)
Citation preview
CONTRIBUTIONS TO CRYSTALLOGRAPHY:CLAUDETITE; MINASRAGRITE; SAMSONITE; NATIVE
SELENIUM; INDIUM
Cuenros PalacHn, H araard Uni,ttersity.
CLAUDETITE
Our knowledge of the crystal form of the oxide of arsenic, claude-
tite, rests chiefly on the study by Schmidtl of crystals formed as
the result of a mine fire at Szomolnok, Hungary' The crystals
measured by Schmidt were mostly paper thin and striated so that
the values recorded are not altogether reliable.
Crystals of claudetite from two sources have recently come into
the hand.s of the author and proved to give such constant and con-
sonant measurements that new elements have been based upon
them. I am indebted to Mr. wilke of Palo Alto for this material.
(o) Cr-auonurE FRoM lupBnral Co., Car,rnonNra:-The hand
and up to 4 mm. long. With the claudetite are crystals of sulphur'
Two crvstals were detached from the wall of a cavity without
distorting them, the extraordinary softness and ease of cleavage
of the mineral making this a matter of great difficulty.
Two excellent crystals were measured, and the angles obtained
from these crystals are shown in the following table.
(D) CrauonurE lRoM Jnnolrn, AnrzoNe:-A small cavity 3 cm'
across lined with beautiful silky crystals of claudetite comes from
the United Verde Mine and is undoubtedly a product of the mine
fire.2 The crystals are plates or laths, terminated only at the free
ends and measuring at maximum 3 by 10 mm. with thickness less
than .5 mm. Both prism and terminal faces give excellent measure-
ment. Four crystals were measured, one of which was a twin on
(100). Table I presents the angles obtained from the claudetite
crystals of both localities.
I Zeit. I?ist., voi. 14, p. 575, 1888.2 See Lausen, C., Hydrous Sulphates formed under Fumarolic conditions at
the United Verde Mine: Am. Mineral', vol. 13, p. 2O3' 1928'
t94
TOURNAL MINERALOGICAL SOCIETV OF AMERICA 195
Tnsrn I
A-Crystals from Imperial Co., California
No. ofForm faces 6
110 5 67"38'101 2 90 00T11 I -66 01111 4 69 24
B-Crystals from Jerome, Arizona
1300 1 1101r01T111 1 1121
p
90'00'37 5140 334449
90 0020 0443 00.t / .).t
40 2944 4846 15
38 4s+12 0089 43
-90 14-65 52
69 2s-48 24
Range <|
67'29',-67"53',89 49 -90 01
69 24-69 25
37 t2 -39 10
89 35 -89 5089 04 -90 3064 43-67 0269 09 -69 3248 00-48 49
Range p
37"47',-37"5s',
M 44-M 53
37 38 -38 0640 17 -40 45u 4045 0346 13 46 18
1022i
1062
The projection elements were calculatedof each locality with the following results:
separately for crystals
Po'qo'
e '
lL
Imperial Co.
.8547
.3487
.075385'41',
Jerome
.8572
.3499
.076185"38',
Mean
.85595
.3493
.07s895040'
From these mean values the following elements are calculated,with which in adjoining column are the elements of Schmidt.
Er,rurNrs op Cr,Lunttrtn
Palache
a:0 .4092 1o :0 .8535c:0 .3493 qo :0 .34839:94"20' p:85"40'
Table II gives the calculated position and interfacial angles ofall known forms of claudetite together with some of the observedangles oI Palache and Schmidt" The table is based on Palache'selements.
Schmidt
a :0 .4040 Po:0 .8527c:0 .3445 qo :0 .34379:93"57' p:86"03'
THE AMERICAN MINERALOGIST
rS 3 tB t 68 33 t 3R$ $11I I g ' g€
sR 88 i3 f ,
r r t $ l t t1x :11" a ' o O No o < t T
N $ ,N N Ir No <
*Ers sgS s+s SSs 8,e sss'*h ' a :Fs $38 RBg I R f , 6R
- dln dlN ild ;lN i lN i lN elf i lN
o e < r a u ? : t : S S R K 5 3 9 5 X S- d ' o I : 4 + r\ i o O ' \ o s O u ? o N 4 \ O N \ q r c A o \ o
a o d N \ o n + - N c o € o o ' + 4 + ? ? *
. . ,Es DBH nSH $;s S$s H:;e" ' hB ssD BEts 3s i l g$9 $98
r r 8 t t 8 t t 1 S i l l i . A= l' 8 I T ;$ B$
' ' g I I n I | 1 $JR 3N I' s E s8e €$l l l
ilN ilN ilN ilff ild iN irNo 4 N € N : - o t 4+ o N 4 n n s - o
i Y : o @ + c \ t N { q . q , qF € h + A S s s v
b o o - S $ " f . = o q - S S e Q r 1 2 { S^ o o o < 1 o i N < s F F e= b o e . D p 9 i B E : ' o - 8 8 9 € $ R6 a i N Q s
| | |
O
t t l l r l
< a ' - |' D O
@ o'1
o
a
o l P '
U
.da
o
;oJd d
(J
Fl
trF
i
z
ts
h
rlOFi
rl
Fi
- 6 o
d i dO O d i N Ni l i i H l d i
q d - - : : Y Y
= = x = ; i 6 ; X = - N < r r6 c i . i ' < N - i i C O C
8s ? : 8 8 8 8 ^ - N < J a
O O U > H , a i t 6 N r a i N d O O Co o : I i . N rd l i l i :
\ s o u * \ S. . a a d: l \ ss a B h I b
JOURNAL MINERALOGICAL SOCIETY OF AMERICA
It will be noted in this table that the aqreement of calculatedposition and interfacial angles with observld angles is for almostall forms excellent. Reference to Schmidt's article will show fur-ther that for interfacial angles his measurements agree better inall cases with the calculated values from the new elements thanwith his own calculated values. There seems no doubt that the newelements are established.
The habits of the claudetite crystals from the two new localitiesare shown in figures I and 2.
Frc. 1
Claudetite, Imperial Valley, Calif .
F rc .2
Claudetite, Jerome, Ariz.
MINASRAGRITE
Minasragrite is a highly hydrous sulphate of vanadium first de-scribed and named by Schaller.s As the name implies, the mineral
3 Schaller, W. T., Minasragrite, a hydrous sulphate of vanadium: Wash. Acad,.Sci . Jour. , vol .7, p.501, 1917.
198 THE AtrIEMCAN MIN ERALOGIST
was found at the vanadium mine at Minasragra, Peru, where it
occurs as a blue incrustation on patronite. Schaller described the
physical properties of the new mineral and assigned to it the form-
ula VzOa.3SOB.16H2O. He found no measureable crystals but de-
termined from its optical properties that it was monoclinic or
triclinic.Specimens of patronite in the Harvard mineral collection, which
in the course of many years have become coated with various al-
Frc. 3. Minasragrite
teration products, showed in places a vivid blue incrustation
which proved to be minasragrite. The crust is composed of minute
but very perfect crystals forming an open net work which falls
to pieces at a touch. Some of the tiny crystals are quite complete
anJ pro.red to be measureable. The two best which were completely
measured, have an average diameter of .2 mm' and a maximum
dimension of .25 mm. Notwithstanding their minute size the crys-
tals gave excellent reflections and proved to be monoclinic' The
habit of the crystals is shown in fi.gure 3. The measured and cal-
culated angles of the forms are contained in Table I. Table II
contains calculated interfacial angles.No close relation in form to any previously described sulphate is
apparent from these angles.Efiorts to prove the presence of any distinct cleavage were not
successful. The crystals were so minute that the handling of them
\ o @ o N
4 4 4 \ O
H H
< 1 o \ N O
S N € SO N D \ O
S t , o r s
S r s - t s
S r s ^ * s
$ N < { o
N E N T
o
bo
o
bo
b0
JOURNAL MINERALOGICAL SOCIETY OF AMERICA
i O d d :
8=5 F , :
^ R ! , 9 H
. S t s ' s a
\ o q s N
" O O N Or i N( : I I I a $
_ r l t t l\ o o oo -
N H o
O N i NN A O +
bo6d^/.
] n s n dS - o 4 v )o \ o o o \ N? ? " ? Y- ' * i No < r \ o 4 bP o * o oO \ O O \ O NO \ 4 N O \ . + '
I
bo
H O i N N
F o o H c )i O N d NN O \ c O c o +
N Ni C )
H N
F8 i l 8N8ER 8$
t l
4 e ;N N X
l l l l n
4 . 5 <
U
! 9 s
SrdSi l r l i< E i $
o 1 2 bN \ o o
[ i l t ls a a a
r-l3
@
z
rl
F
z
4
J
Fr
N 6 ;O \ 4 N
N O :D O ' T
O O NN O \ c O
o
z
2OO THE AMEKICAN MINERALOGIST
was difficult. There seems to be a tendency to break in the general
direction of the side sinacoid but with no true cleavage parallel to
that plane as Larsen suspected on optical ground.
SAMSONITE
The crystal form of samsonite has been described by three
authors whose measurements yield closely agreeing results. W'
Bruhnsa calculated elements from three angles between two forms'
His position differs from that adopted by later observers and
here used. Calculating his measurements to the new position, we
obtain the elements:-
a : 1 . 2 7 8 7 , c :0 .8204, F:92"42'
F. Slaviks gave a fuller description based on the measurement of
many crystals. His elements, derived from three angles between
three forms, are:-
a : 1 . 2 7 7 6 , c : 0 . 8 1 8 0 , F:92"46'
The third description is by F. Kolbeck and V' Goldschmidt,G who
measured. six crystals on the two-circle goniometer. The elements
calculated from their two best crystals are:-
a : 1 . 2 7 7 7 , c --0.8192, A:92"42'
The author measured. five crystals, also by the two-circle method
and his calculation yielded the elements:-
a : 1 . 2 7 8 6 , c : 0 . 8 2 1 7 , B:92"3+'
Since these four independent values for the elements are in such
close agreement, it was felt that the mean of all of them was better
than any one. This mean value is as follows:-
a : 1 . 2 7 8 2 ,Ps :0 '6414,
c :0 .8198 ,qs :0.8189,
B:92"4I 'y ' :87" 19'
An angle table was calculated from these elements and has been
published elsewhere.T Table I contains the position-angles for all
a Kristallform des Samsonit von St. Andreasberg, Itrl Jahresb' il. Niedersdchs'
geol,. V ereines, E annoaer, l9ll.5 Morphologie des Samsonits, Bull. internat. iJe l'ocad" des sciences de Bohame,
1911, p. 16.s Ueber Samsonit von Andreasberg, Zeit. Jiir Krist-, vol,50, p. 455, 1912'7 Crystallographic Angle-Tables, 1933. Dept. of Mineralogy, Harvard univer-
sity, privately printed.
,TOURNAL MINERALOGICAL SOCIETY OF AMERICA
^ :x x
s i D . r - I
4 < r d 1 - - I
- l -
l - - \ o i o \ * *
|4 + < 1 * -
I - l -
H O m d f r6 b o 6 6 6b o > b o b o b o
: !* o
.o .!: t lz "E
N c o r + N , 4 n. + l o h I s i + | N €< ] < t o N 4 i d l* o s N < { \ o \ o- l t l t l@ € O \ t D , 4 € +H N + I N I N I € N
< t < 1 o N r ' ) o +H O S N $ \ O €
t l l
r l l
I I I
t t l
I t t
t t t
e . - C ) l c ) | - l N O
q q . q . c . N Nr l t l
o N N O O c tO O I O I . + l O o
o o o q o NO \ O \ 0 1 O N N
I I
I I
=f cO cO. o l o s< 1 0 0 ' 6- i TTi , e n* l s a< 1 N \ Oi c a 4
b0
a
E
< x
a
a
N , N N e - S 5 . S @v : : = s I o q 4 i N
I o l o NN + r < r o N N 4 < rN : S O \ O N + \ O \ O
, i - . o D o \ N i o , < , $ " o i N \ o # al ; - = N s o o r I o o o o o I o I * 4
E ) N d r i N o o + o o o o o \ o o Nq * d N e q O \ O \ O 1 O \ O \ O N N
l l l l t l
ilN ilN ilN ilR {d HIN Hld4 9 N + \ O O N r N O O N
. N N O O $ T , N 4 N + H' o o . ' + + o : N \ o D € o +
N S - € S \ O N < t + C \ O \ O
o!
a
Q\ dIN F'N /IN Ftr
a a + € . 4 + N : \ o o o N o , 1 D N \ o
" o o o e a N o N s ; O * 6 = = O 4 - r h q
O Q : < ' : c O N \ O o c ) O O 4 O \ o \ Nq i i N Q 4 o \ o \ d l s 4 i Nt t t l
v , r i s i i i N i= t o s Q N i i i i o o o o c ) i * H Na i i - i d N O O i i H l c r ! f O i l H N l i
€ t s u o S S s " a . e \ \ $ s * q F r t t
N
|.+t
TH E AM ERICAN MI NERALOGIST
the forms hitherto observed and, for the forms observed by the
author, the measured angles.In Table II there are shown the forms found by the various
observers.
Tasr,n II
Bruhn'ss1'rnbol Slavik Kol. & Cold. Palache
b
aq
IkT
010100140
xx x
?
s t J ( ,
n 120tn 110
?
x
x
203T01001
?
xx
2ro0120 1 1
)
x
3015011 1 1
1 1 12 1 2T2T
47s
xx
x
It is somewhat remarkable that the forms observed by the four
observers are so difierent, for the mineral samsonite seems to have
been found in only two vugs in the Samson shaft at the St' Andreas-
berg mine and one would. expect more uniformity in the habit of
the crystals. The total absence of the orthodome forms on the
crystals of Kolbeck and Goldschmidt is in strong contrast to their
strong development in all others measured. The author's study
103101I01
Jd
hp
Forms of Samsonite by various observers
JOURNAL MINER.4LOGICAI, SOCIETY OF AMERICA 203
establishes (130) as a well-developed member of the form seriesand adds the two f orms fr(O12) and x(l2l), both weakly developed.
NATIVE SELENIUM
The element selenium has never been certainly identified as aminerall nor have crystals of the metallic gamma-selenium everbeen made artif icially which were accurately measureable. Muth-mann8 has, it is true, f igured a combination of prism and rhombo-hedron of this substance, but the figure is based on approximatemeasurements on the microscope stage of the edges of minutecrystals, and these measurements by no means justify his assertionthat selenium is completelv isomorphous with tellurium.
Much interest, therefore, attaches to specimens of seleniumfound in the fire-zone of the United Verde Mine which, like theclaudetite already described, were secured through Mr. Wilke.
There are several hand specimens of quartzite and of fire-frittedsandstone partly encrusted with needles of selenium. The needlesmay reach a length of 2 cm. with a diameter not over 1 mm. Some-times they are clustered in flattened sheets parallel to a prismface so that patches up to 5 mm. across reflect together. On onespecimen the selenium is in melted films or in droplets of dark redglass. Loose crystals up to 2 mm. long were also present and whileclearly of hexagonal form were generally bent and twisted so thatthey could not be measured. Many of the crystals were hollowand tube-like with facets on the edges. A few tiny crystals about.5 mm. in Iength proved to be undistorted and gave excellent re-flections on the goniometer. They always showed the prism of lhefirst order, m, and a rhombohedron. On the best crystal faces ofother forms were found. The table shows the observations madeon this crystal.
No' of Measured Calculatedf a c e s 4 R a n g e p R a n g e Q p
ln 1010 5 30'02' + 11' 90"00' 0 30'00' 90'00'a l l20 2 0004 + 1 u 0 000h 2130 4 1922 +15 u 0 1906r l0l l 3 -30 07 111 52 40 +4' -30 00 52 28
e ol12 | 29 17 34 20 30 00 33 13
J 1123 1 o 06 37 33 0 oo 37 0.5+
8 Zeit J. Krist., vol. 17, p 357, 1889.
204 TH E AMERIC.IN M IN ERALOGIST
The mean angle p of the unit rhombohedron from the seven bestreadings on four crystals is 52o38' with a range of 52"36'-52"43'.Calculating from this angle, we obtain the axial ratio and angles
shown below in comparison with those of tellurium.
Se
Te
c
1 . t34I .330
2o0.75500.8867
c A r
52'38's6 ss+
rAr
86"59;',
93 03
Frc.4. Crystal of Native Selenium showing the forms zz(1010) and r(1011).
Two crystals showed minute faces in the position of the nega-
tive rhombohedron. It was impossible to determine whether these
were due to twinning on the vertical axis with complete penetra-
tion or to the normal development of this form. Figure 4 shows,idealized, the habit of the average crystal.
Cleavage of good quality was occasionally visible but, becauseof the softness and extreme flexibility of the crystals, it was very
difficult to develop it without rendering the crystal unmeasure-able. Approximate measurement showed, however, that it was
JOURNAL MINERALOGICAL SOCIETY OF AMERICA 205
parallel to the negative rhombohedron e(0II2). fn tellurium thecleavage is prismatic and basal, another point of difference betweenthe two elements.
A sample of the very homogeneous crystals was analyzed byF. A. Gonyer and proved to be without a trace of tellurium and tohave but a trace of sulphur.
INDIUM
A sample of crystallized indium, prepared in the Harvard Chem-ical Laboratory by Chester M. Alter in 1932, was studied by Dr.M. A. Peacock. The sample consisted of arborescent groups ofbrilliantly silver-white crystals. Some of the groups were severalcentimeters long, but the individuals composing them were lessthan a millimeter in any dimension. The substance is.so soft andwax-like that only occasionally could a crystal be detached withoutdistortion. The symmetry proved to be tetragonal with close ap-proach to isometric form. The angle cAp, (001)/\(111), is 56o35', the mean of nine measurements with the range 56"10'-57o00'.The value of c calculated from this angle is 1.072. The forms ob-served are c(001), o(100), m(lI}) and p(111). The arborescentgroups were largely developed by elongation of the crystals parallelto an o-axis.