PRECIOUS &
RAJASTHAN
SEMI-PRECIOUS
STONES
IN
INTRODUCTION
The minerals having special physical ,properties like beauty, purity, durability and rarity
are classed as gem stones. India has been recognised since ages, as one of the most
important gem bearing areas of the world and has been producing a variety of precious
and semi precious stones such as diamond, ruby, sapphire, emerald, chrysoberyl,
alexandrite, aquamarine, topaz, amethyst, garnet moon stone, sunstone etc. Most of the
Indian precious and semi-precious stones produced have been readily marketed in the
international market fetching attractive prices.
GEMSTONE RESOURCES OF RAJASTHAN
Rajasthan is endowed with rich potential of precious, semi-precious and ornamental
stones. The most important stones that could be mined and marketed may be classified as
follows.
(1)
PRECIOUS STONES: Emerald, aquamarine and Chrysoberyl.
(2)
SEMI-PRECIOUS STONE: Amethyst, garnet, coloured tourmalines, staurolite,
kanite, andalusite, apatite, sphene. iolite, gedrite and quartz.
A brief descritpion of some of the precious and semi-precious stone occurrences are
given below:
(A) PRECIOUS STONES
(i)
EMERALD: It is the most valuable of all precious stones and is a transparent
variety of beryl with the well known emerald green colour. In India emerald production is
reported from Rajasthan alone. First discovery of this precious stone was made in 1973
by a private prospector in Kalaguman area. Subsequently the discovries of emerald
deposits at Bubani, Rajgarh, Tikhi and Gamguda were made.
Rajasthan emerald belt extends for about 185 km. from Gamaguda in Rajsamand district
to Budani in Ajmer district. In all these occurrences the geological"melien" is idential and
is restricted to the contact of beryl beari ng pegmatites and the metau Itramafites. The
concentration of emeralds are found to be very sporadic and highly variable. The crystals
are often fractured and enclose fine dusty or veil like inclusions.and the flawless dark
green completely transparant crystals are very rare.
Prospecting for emerald was done by National Mineral Development Corporation
in 1969-70 around Gamguda by pitting and trenching but with out much success. The
Geological Survey of India also did some work in 1976-77. The state Department of
Mines & Geology also carried out investigation around Ghata, Thoria and Padasli area of
Udaipur district in June 1979 to evolve some quide lines for emerald prospecting.
ii) CHRYSOBERYL: Greenish yellow to honey brown transparent chrysoberyl has been
reported from the beryl bearing pegmatites near Govindsagar in Kishangarh area and also
from Lohagal near Ajmer. The possibility of its association with the beryl bearing
pegmatites of Ajmer Rajnagar emerald belt is bright.
(B) SEMIPRECIOUS STONES
(i) GARNET: Rajasthan enjoys monopoly position in India in garnet of gem variety. The
mineral is almendine garnet of red and violet or purple colours. Garnet deposits are
located at several places in Ajmer, Bhilwara, Rajsamand and Tonk districts. The most
important gem variety garnet is found in Tonk district. A 11 km. long belt runing NE-SW
to N-S exists between Kalyanpura to Rajmahal in Tonk district where most of the garnet
mines are located. Besides this belt, scattered occurrences are at Ragunathpura,
Raote, Tordisagar and Bagri. The total length of garnet belt from Mavl in Udaipur district
to Bagri in Tonk district is nearly 250 km. with varying width of 17 to 40 kms. The
garnet is found associated with medium to high grade regionally metamorphosed pelletic
sediments of Aravalli age.
II) EPIDOTE: Epidote with its pistachio green colouroccurs associated with
chrysoberyl near Govindsagar, Sarwar and north of Marwar.
II) TOURMALINE: The tourmaline occurs localised within the pegmatites which
intrude the volcanosedimentary sequences of the Aravalli and Delhi Supergroup as
well as the units of the Banded Gneissic complex over a strike length of 300 km. from
Jaipur to Udaipur through Ajmer , Bhilwara , Tonk and Pali districts distributed over a
wide zone of 100 km in an approximately NNE-SSW direction. Though gem quality
rubellite and other blue-green and yellow varities have not been reported, from several
localities.
III) AQUAMARINE: Aquamarine is the sea blue or sea green variety of beryl. The
yellow beryl is known as Heliodor. All these varieties have been found in Toda
Raisigh Bagri, Hamirpur, Bilaspur, Hanotia, Jhopra and Botunda localities of Tonk
district.
The State Department of Mines & Geology carried out investigtions in BotundaToda Raisingh area during 1969-70 and 70-71. Some more work was done in June
1979 to March 80 and on the basis of that work it has been seen that the areas falling
north of Toda Rai Singh are most promising while areas near Lakholai and Baori
villages are also potential.
IV)AMETHYST: The mineral quartz occurs in numerous forms and beautiful colours
which are used as semi-precious stones. Amethyst is purple
or violet coloured crystalline variety of quartz. Occurrences of amethyst in Rajasthan
have been reported from Singhana (jhunjhunu), Kishangarh(Ajmer) Niwai (Tonk),
Isarda( Sawai-Madhopur)
V) TOPAZ: Geological survey of India has reported presence of topaz in Sirohi area
during investigation for wolframite.
VI) CORUNDUM: Corundum deposit in Rajasthan is reported only near villages Juali &
Hanotia in Tonk district Corundum crystals in Juali area are found occuring as
dissemineted grains and crystals at the contact of schists with pegmatite intrusions.
VII) ALUMINO-SILICATE GEM: Gems quality Kyanite, granulite and andalusite occur
over wide areas within the metamorphosed pelitic to psammopal itic assemblages of the
Aravalli and the Delhi Super groups as typically seen in the Khetri copper belt.
Cruciform andalusite (Chiastolite) has been reported from the Khetri-Kolihan belts.
VIII) CORDIERITE-GEDRITE ROCKS: Cordierite gedrite rocks, associated with Khetri
copper belt form excellent semi precious stones. Large acicular stellate aggregates of
gedrite/anthophyllite set in a cordierite rich matrix takes good polish and can be used in
the manufacture of ash trays, beads and other fancy items.
IX) APATITE & FLUORITE: Apatite and fluorite some times used as semi-precious
stones due to their, beautifuJ coJour5. Apatite generally occurs in green colour where as
fluorite occurs in various shades of green, blue, violet, white and colourless varities.
Occurrrences of apatite are reported from Sikar and Udaipur district, while fluorite are
from Jaipur , Sikar, Dungarpur and Jalor district.
GEOLOGICAL 'MILIEU' FOR GEMSTONE
The gemstones occur in diverse geological'milieu' but remarkably localised in the high
grade Archaean granulire belts of India. Burma and Sri Lanka. Some of the important
precious and semi precious stones that occur are given in the Table-1
GRADING OF GEMSTONES
The commonly accepted grade of precious and semi-precious stones as per international
market demands are the following:
1. FACT GRADE: Perfect colour, transparency, hardness and flaw less gems.
2. CABOCHON GRADE: Slightly inferior in quality, in colour and transparency. The
asterated and chatoyant stones should have the required optical effect to produce
"Star" or Cat's eye' effect.
3.CARVING GRADE: Gems with exceptional size, colour, transparency and should
with stand to carving or engraving.
4.TUMBLING GRADE :Translucent to opaque stones with flaws and enclusions are
included.
5. RUN-OF-MINE GRADE: Includes all grades
(Grab lots)
SCOPE FOR GEMSTONE-BASED INDUSTRIES IN RAJASTHAN
Jaipur is world famous for cutting and polishing of coloured precious gems as well as the
manufacture of a variety of semi-precious stones on a large scale. Thousands of
artisans are engaged in processing of all kinds of precious and semi-precious stones
such as emerald, ruby, sapphire, chrysoberyl, alexandrite, aquamarine, amethyst,
garnet, iolite, moonstone, sunstone, star diopside, star ruby, enstatite-cat's-eye, bronzite,
labradorite, etc. Excellent carving work is also carried out from all types of gems. Jaipur
is famous for quality cutting and carving. Manufacture of beads from a variety of semiprecious stones and manufacture of fancy items such as ash trays, cameos, is carried
out on a large scale. In recent years, Jaipur has taken a lead in the export of precious
stones studded gold and silver jewellery and also silver jewellery made out of cheap
semiprecious stones and has contributed in a spectacular way to the achievement of
Indian export of gems and jewellery.
SCOPE OF DEVELOPMENT
Precious and semi-precious stones are being processed in most of the places in Jaipur
manually by several thousand skilled workers. It is understood that large scale
production of beads, faceted and cabochon gems is carried out under the direct
supervision of the manufacturers or exporters. Semi-precious stones such as garnet,
amethyst, moonstone, etc. are given to outside artisans for the ,manufacture of beads,
ash trays, etc. By this methods of manual processing, the cost of production per carat
cannot be brought down when compared with the manufacturing costs seen in Japan,
Germany, Taiwan, Thailand, etc. There is lot of scope in the following fields:
1. Faceting of Transparent Gems.
2. Bead making equipments
3. Carvi ng
4. Cabochon making.
Statistical Information for Gem stone In Rajasthan.
S.No
Mineral
No.of leases
Production
Sale Value
(Thosand Rs.)
1.
2.
Aquamarine
1
Emerald
3
Nil
3.81Kg.
Nil
22860
3.
Beryl
-
4.
Gamet:
Gem
585.0Kg
216.0Ton.
73.12
216.0
Abrasive
9
Revenue
Nil
2.0
47.59