THAILAND’S RUBY AND SAPPHIRE DEPOSITS

• - In lateritic soils atop Plio Pliestocene ba salt, or in gem gravels derived from basalt

- . Deposits are about 6 2 0 ' below the surrrrrr • Source is thought to be basalt (corundur rrrrrrrrrrrrrr • Mining restricted to Thai nationals since1919.

• - - 8 5 9 0 % from the Chanthaburi Trat gem field (since 1 8 5 0 ?),

• r rrrr rrrrrrrrrrr 7 0 % .• Darker red; brownish to purplish overto

ne r uby due t o Fe

• - More Fe rich than Burma ruby, show ar rrr r rrrrr rrr rrrr rrrr rrr rrrrrr rr shortandlongu.v..

• rrrrrrrrrr rrrrr rrrrrrrrr().

Present situation !

Hughes, R.W. (1996) Ruby & Sapphire.RWH Publishing, Boulder, CO, 512 pp.

Map of Corundum sites in Thailand a nd Cambodia. (Modified by R.W. Hu

ghes from Vichit & Vudhichativanich et al., 1 9 7 8 )

A miner works with traditional methods at Kha o Ploi Waen, just outside of Chanthaburi. Mech

anized mining has resulted in rapid depletion o f most mines in Thailand, making miners such

as this an endangered species. A handful of r ough sapphir

es from Khao Ploi Waen.

A ruby mine near Tok Prom. Today it is operated mainly for tourists, and will soon close. (Photo: R.W. Hughes; Jan., 1996)

Thai military sign ou tside Bo Rai forbiddi

ng declaring that en try into the area wit hin five kilometers o

f the Cambodian bor der is restricted to t

hose with military p ermits. According to

one villager with wh om the author spok

e, this zone contains a number of

Khmer Rouge camp s, but this was denie d by military official s along the border.

(Photo: R.W. Hughe s; Jan., 1 9 9 6 )

The early mo rning rough r

uby market a t Bo Rai, in Tr

at province, T hailand. Whe

re once close to a thousan

d people gat hered to trad

e gems, toda y only a few s

tragglers rem ain.

(Photo: R.W. Hughes; July,

1996)

Vietnam produces rubies as good as anything from Burma. But the machinations and intrigue surrounding the gem business in that country have left this potential largely unexploited.

-http://www.ruby sapphire.com/vietnamese_rubies.htm

VIETNAM

Map of northern Vietnam, showing the location of the important ruby mines at Quy Chau and Luc Yen.

Like ruby mines in Thailand and Cambodia, bulldozers or backhoes are used to excavate the land. The earth is then forced into a separation jig by the use of water cannons. Once in the jig, the “heavies” (higher density minerals) are sorted by hand to remove the rubies. Nominally-illegal pit mining is also carried out throughout the district, mainly on the fringes of the mechanized mines.

Corundum deposits of India

Sapphires from the famous Kashmir mine- - - -http://www.ruby sapphire.com/r s bk india.htm

Reprinted from Records of the Geological Surv ey of India. Vol. 23, Pt. 2, May, 1890, pp. 59–6

9

http://www.palagems.com/kashmir_sapphire.htm

The location and geology of the famous Kashmir sapphire mines near Sumjam. The sapphires of Kashmir occur in outcrops high on the wall of the Kudi Valley. Within an actinolite-tremolite rock, small pegmatite lenses occur, and it is within these lenses that the sapphires are found.

View of the Kashmir sapphire mines taken in 1887-8.

- A 3.03 ct Kashmir sapphire illustrate

s the color and vel vety texture which

has made stones f rom this locality so

famous.

Kashmir sapp hires, such as

the stone abo ve, are often cut as sugarlo

af cabochons. Note also the

blackish color , which many

Kashmir sapp hires display.

- This 4 ct. plus Kashmir sa pphire exhibits the velvety

blue color that has made s tones from this source wit

hout peer in the world.

The sapphire washing apparatus constructed at the Kashmir mine taken in 1887-8.

The famous Kashmir sapphire mines produce two different types of rough. Some of the crystals display heavily corroded surfaces, while in others the original crystal surfaces are largely intact.

The color in Kashmir sapphires lies mainly alon g the crystal faces, with the core of the crystal

being colorless. Unfortunately, in the corroded crystals this vital color layer is largely absent, making them poorly suited for cutting. Both cor

roded and uncorroded crystals have proven sat isfactory for heat treatment.

Mining methods at the Kashmir mines have always been primitive, due to the altitude and remote location. Today, the mines remain accessible only by foot or helicopter.

At first, huge quantities were obtained by simple digging.

Since 1927, the mines have been worked intermittently, but with no real success. Every few years the Kashmir Government makes noises about leasing out the mines, but so far these attempts have not come to fruition.

Top right: Healed fissure with flat, strongly recrys tallized cavities (negative crystals) in a Kashmir sa pphire. Some of these cavities contain tiny opaque crystals of unknown identity. 5 0 x.

Below left: Pargasite crystal in Kashmir sapphire. Below right: -Tiny hexagonal crystals with thin fil

m satellite haloes in a Kashmir sapphire. These are similar to those found in Thai/Cambodian rubies. ( Photos: Henry Hänni/SSEF)

Blue velvet--inclusions of Kashmir sapphires

Top left: Most di stinctive of the K

ashmir sapphire inclusions are th

e rounded zircon crystals with tiny

accompanying bl ack uraninite cry

stals.

CORUNDUM DEPOSITS

OF SRI LANKA

Sri Lanka Corundum Deposits

• Sri Lanka and has supplied the world with fine R ubies and Sapphires for over 2 ,0 0 0 years.

• All varieties of Corundum are found in Sri Lanka i ncluding the "PADPARADSCHA " which is unique to

the island.

• Main deposits (gem gravels) in the Ratnapura dis trict, about 1 0 0 km S.E. of Colombo, and Elahe

r a district (1 1 5 km NE of Colombo).

• Rubi es are typically more pinkish (could be referred to as pink sapphire

in some cases) than those of Burma or Thailand. C haracterized by 1.) sparse, long, rutile inclusions,

and included zircons with radiation halos. 2 .) give - off a strong orange red in long u.v. light. and 3 .) e

xceptional star stones.

• The Sri Lankan gem gravels also produce zirc on, tourmaline, peridot, quartz, garnet, feldspa

r and a number of other stones.

• Mining in Sri Lanka is mainly alluvial with gemdeposits found not only in present river system s but also below rice paddies where ancient riv

ers once flowed.

• The depth of the gem gravel or "ILLAM " varie s f r om3 m t o20m to as much as 4 0 m at

Pelmadulla.

• The search for gems is a highly speculative o peration and is usually carried out by a group o

f native workmen on a share basis. 15/ th goe s to the owner of the land , 15/ th to the financ

i er and t he r est goes t o t he wor ker s.

Traditional gem mining in Sri Lanka

Open-pit mine in

the Elahera area

Mining areas

around Elahera

http://www.cigem.ca/srilanka/sri.html

Active open-pit mine

The gem-bearing level

has been reached

http://www.cigem.ca/srilanka/sri.html

Washing off the illam to

filter out the gems.

The miners are extracting the

gem-bearing gravel (illam).

http://www.cigem.ca/srilanka/sri.html

Washing the gem gravel

in baskets

The washing area is often

separated from the mining

area.

http://www.cigem.ca/srilanka/sri.html

Sapphire Deposits of Australia

Queensland (1870) : Anakie and Lava Plains districts; New South Wales (1960) : Glenn Innes and Inverell districts

• Gem dirt (alluvium) at the surface, to 50 ft. thick atop weathered basalt. • Anakie noted for fine yellows, also some very fine blue but most has been characterized as "inky" (too dark) or strongly dichroic dark blue and green; some production of pink and orange as well. • Dark sapphires are bought by Thai dealers and others who lighten the color by heat treatment.• Currently a major producer (50-70% of world production in 1990).

Sapphire Deposits of USA

MONTANA : Missouri River, NE of Helena, also Yogo Gulch, near Utica

• Mined (Missouri river gravels) intermittently from 1865-present.

• Sapphires usually quite small, well-rounded or flat, and of a pale blue or blue-green color.

• Yogo Gulch blue sapphire are said to rival Kashmir for color

• Yogo Gulch mine is in 2-8' wide dike that cuts limestone.

• Hard rock mining techniques and American labor makes mining relatively expensive, less economic than East Asian counterparts.

• Geological surveys indicate a minimum of 28 million carats are still in the ground, making this one of the largest proven deposits in the world.

Sapphire from the Missouri River in Montana

•Umba River Valley near Kenyan border; since 1962.

• Sapphire in a "corundum pipe" (dike?, basalt flow?)4 miles in diameter.

• According to one source, the market in "East African" corundum was cornered in 1965 by a group of dealers; most rough still uncut.

• Noted for past production of fine orange-pink, deep purples, dark, untreated golden yellows, and color-change (i.e. alexandrite-like) sapphires.

Sapphire Deposits of Tanzania

Sapphire Deposits of

Madagascar

The discovery of sapphires in Madagascar is relatively recent.

The first report of the existence of this beautiful gem was in 1952 when a French geologist noted the presence of small sapphire crystals.

In 1982 local traders offered the first commercial packages and a disorganized rush ensued.

There are three distinct types of layers:

•Layers found in metamorphic rock. These being primarily found in the northern parts of Madagascar (Anivorano), in the central part (Antanifotsy, Faratsiho and Moramanga).

•Layers of alluvial deposits, which are located in the regions of Ranohira, Ilakaka, Bezaha and Sakaraha (the southwastern part).

•And the layers in marble, which are located mostly in the south (Andranodambo). The marble being of a limestone derivative rich in aluminum oxide.

• Sapphire district in northern Madagascar has significant quantities of sapphires, many of which were produced by artisanal miners in the most primitive of methods. Some stones are of large sizes, 5 gram to 20 gram (25 to 100 carat sic), being common.

• In the early nineties, deposits were discovered in the southern part of Madagascar (Andranodambo).

Since 1996, large quantities of yellow to blue sapphires have been recovered from alluvial deposits derived from basaltic rocks in northern Madagascar. The crystal morphology, internal growth patterns, mineral inclusions, absorption spectra, and trace-element contents of these northern Madagascar sapphires are typical of “basaltic-magmatic” sapphires. Comparison of the properties of these sapphires to those of sapphires from different basaltic sources reveals no significant differences. The northern Madagascar sapphires are distinct from those from Andranondambo, a skarn-related deposit in southeastern Madagascar.

Sapphires from Antsiranana Pro

vince, NorthernMadagascar

Dietmar Schwarz, Jan Kanis, and Kar

l Schmetzer Gem& Gemology,

Fall 2 0 0 0 , Vol ume 3 6 Issue

3

The biggest rush on the island however, was caused by the discovery in 1995 of blue sapphires in the northern part of the island (Anivorano) of medium "Ceylon" quality.

Then very fine blue, pink, blue-violet, violet, purple, orange and yellow sapphires were discovered from a new alluvial deposit in the south-west, in Ilakaka, at 80 Km from Sakaraha or 210 Km from Tulear, 3 hours drive.

http://www.gmrcorp.com/

The Ilakaka booming city.

Natives coming from all over the island set up very precarious shelters, hoping to rapidly discover the magic stone and therefore, move to another way of life

Ilakaka area: flat, vast and basically free of trees

There are an estimated 300,000 hand-miners in the Ilakaka area working in the field at present day.

The booming community in Ilakaka has sprung up within 3-6 months around the sapphire mining.

They use shovels and buckets to excavate their digging-holes. The gravel is loaded into bags and carried long distances to the nearest water-source for processing.

They are digging on the surface deposits, which are extremely rich. Some adventurers dig up to 15 meters below the surface, risking their lives every second.

• The mineralization of the sapphire (blue, violet, pink and translucent) and the accompanying minerals (zircon, spinel, garnet, topaz and chrysoberyl) are found in the upper and lower terraces.

• The layer commonly known as "lalambato" in the region, is a layer of stones of many different sizes mixed in with other blocks of rock of various types and medium-grain sand.

• The useful minerals are mostly concentrated below the layers consisting of blocks of rock.

Hand-miners digging-holes, up to 15 meters below the surface, tremendous risk to try to get rich quick.

#http://www.gmrcorp.com/page/ilakaka.html

Test digging showed sapphire formation with limestone and basalts.

http://www.royalgemscorp.com/

Sapphire Deposits of

North Madagascar

Magnificent rough sapphire from Northern Madagascar. 38 grams, 190 carats, field cost $3,000 U.S., estimated value when cut $50,000

Larger sizes of rough sapphire before heat treatment

http://www.royalgemscorp.com/

Heat treated opaque grade, cuts into cabochon star.

http://www.royalgemscorp.com/

Average grade melee of heat treated and cut sapphires.

http://www.royalgemscorp.com/

Sapphire from Helena, Montana (El Dorado Bar)

UNITED STATES

Montana produces sapphires as fine as any in t he world. Not far from Utica, Montana, a sapphi- re producing lamproite dike cuts through the c

ountry rock for almost five miles. Discovered b y a prospector, Jake Hoover, in 1 8 9 5 , the Y

ogo Gulch mine went on to produce hundreds or rrrrrrrrr rr rrrrrr rr rrrrrrrrrrr-rrrrr rrrr gemstones. Most are alluvial deposits such as those

along the Missouri River near Helena

, or Dry Cottonwood Creek near Butte . Cur rently, the largest sapphire production is coming from the Gem Mountain

area near Philipsburg .

Many of the Montana sapphire fields have been open to amateur collectors on a fee basis. El Dorado Bar is an ancient gravel bar lying above the Missouri River not far from Helena, Montana. To find sapphires at this location the collector first screens the gravel to remove over-sized and under-sized materials (Most sapphires at this site are larger than one-sixteenth of an inch, and smaller than one-quarter of an inch in diameter). The screened gravel is then moved to a suitable water source where a heavy concentrate is made by either mechanical or hand jigging. The jigged concentrate is then hand sorted in the hope of finding gem sapphire.

B.) Jigging the size-classified gravel to concentrate the sapphire, garnet and other

heavy minerals toward the bottom center of the boxed screen.

BA

A.) Digging and screening the sapphire-bearing gravel to remove the over-sized

rock and under-sized sand: El Dorado Bar, Montana

Digging for Sapphires at El Dorado Bar, Montana

- After the sapphire bearing gravel has been concentrated by jigging in water,

the gravel is flipped on a table and car efully hand sorted to identify the wate rworn sapphire crystals. Mostsapphire

s from this area are a pastel blue or bl- ue green color, butvibrantpurple, pin

kand even red stones have been foun d. The rough sapphire crystals and fra

gments from El Dorado Bar are genera lly less than 5 carats in weight, but th

ecl ari ty of the gemmateri al i s verygood.

A .) Picking through the concentrated gravel for gem sapphire: El Dorado Bar, Montana

B .) Typical waterworn sapphire crystals (note th - e hexagonal cross section of some pieces) from El Dorado Bar, Montana

A B

A 3.5 Carat Faceted Sapphire from El Dorado Bar, Montana

Sapphire from Gem Mountain (Rock Creek Area), Montana

UNITED STATES

SapphirewasfirstdiscoveredinMontanainthelate1800'sbygoldminersworkingthealluvialgravelsoftheMissouriRi ver near Hel ena.I n1 8 9 2 gold prospectors discovered th

e Gem Mountain sapphire deposit; one of the largest sapphire deposits in the

world. The famous Sapphire and Anaco nda Gulches atGem Mountain were so rich they were mined exclusively for ge

mstones. Since 1 8 9 3 this mine ha sproducedareported180mi l l i oncarats of sapphi re.

Sapphires were mined at Gem Mountain continuously from the turn of the century until the second world war. It wasn't until modern heat treatment processes evolved that Montana sapphire production skyrocketed. In 1991 a young state senator from Minnesota, Greg Dahl, began acquiring mineral rights in the Rock Creek area. In 1994 he purchased the Gem Mountain sapphire deposit. In 1994 Dahl's company, American Gem Corporation, went public. Since then the corporation has done a great deal of discovery work on their properties, they have completed construction of a new plant and mine on the Anaconda Bench on Gem Mountain, and have pursued an aggressive expansion plan for production, cutting, and sale of fine sapphires.

Thegemstonesfromthislocationarerelativelysmall,buttheircolorandclarityareextremelyfine.Colorsincludered,orange,yellow,pink,green,bl ue,andmany combi nat ionsofthosecolors.Manycrystalsthatdonotnaturallypossessgoodcolororclarityare heat treatedunder carefu llycontrolledconditionstoimprovetheappearanceofthefinishedgemstones.PrecambrianandTertiarydeposi ts aroundGemMountai nh avebeenerodedtoreleaseandburythesapphirecrystalsunderlayersofgravel .The gravel s andsands th atcontainthesapphireconsistofquartz,sandstone,chert,dolostone,maficvolcanicsandi ntrusi ves,andandesi te a ndrhyoliticrockfragments.Formanyyearsporti ons of the GemMountai nsapp hiredepositwereopentoamateurcol l ectors ona fee basi s (At one ti meitcost$60perpersonper day!).

The Gem Mountain stones display a remarka ble range of colors including blue, green, pin

k, and gorgeous yellows and oranges. Furthe r stimulating the sapphire "boom" in Montan -a is the application of advanced heat treatin g technology that can remarkably improve th e clarity and color of many Montana stones (

Don't get upset: heat treatment has long bee n a standard practice in Thailand to turn ugly

Sri Lankan gueda sapphire into fine blue gem material. )