SILICA MINERALS: SILICA SAND, QUARTZ,
QUARTZITE & JASPER IN RAJASTHAN
INTRUDUCTION
Silica (SiO2) is one of the ubiquitous material in the earth's crust. Quartz, quartz crystals
quartzite, silicasand and moulding sand are all grouped together under one genetic name
"Silica minerals".
Broadly, the silica minerals can be grouped under three categories i.e. crystalline form of
silica, cryptocrystalline varieties of silica and clastic or granular varieties.
Crystalline form of silica: Quartz is the crystaline form of silica. It has hardness7; Sp.Gr.
2.63 and is generally colourless when pure.
It is resistant to weathering and insoluble in acids except hydrofluoric acid on heating,
ordinary or low temperature quartz (q-Quartz) inverts at 575°C to high temperature
quartz (p-Quartz) which begins to invert at 870°C to Tridymite and this at about 14700C
passes into crystobalite and finally to a silica melt at 1710° to 1756°C.
The important varieties of crystalline quartz are : vein quartz (massive crystalline quartz);
Milky quartz (white, translucent to opaque); Ferruginous quartz (containing brown
limonite and red heamatite and almost opaque); Aventurine quartz (containing glistening
flakes of mica or heamatite); cats eye (opalescent greenish quartz with fibrous structure);
rock crystal (clear, colourless well-crystallised transparent quartz); amethyst (clear,
purple or violet blue) transparent quartz besides, rose quartz, smokey quartz, etc.
Cryptocrystalline form of silica: This group includes; Chalcedoney, Agate, Tarper,
Onyx, Flint & Chert etc.
These forms appear non-crystalline (amorphous) in hand specilnens, but under
microscope show double refraction and this reveals their concealed crystalline nature.
The different transparent and translucent varieties of silica are valued as semi-precious
stones and are carved out into variety of ornaments and used for making ornamental
wares or decorative articles.
Clastic or granular varieties (Silica sand) : Silica sand consists largely of unconsolidated
quartz grains of size varying normally between 0.06 to 2 mm diameter. It is formed
chiefly from the weathering of cemented sand stone, felspathic rocks & quartzites. Silica
sand mostly contain 85 to 98.8% Silica (SiO2) but impurities are the prime factor for its
gradation for use in various industries.
According to suitability names as building sand, paving sand, moulding or foundry sand,
refractory or furnace sand, engine sand, filter sand, glass sand, grinding and polishing
sand are in prevalance. Sand is also used as fire proofing material for sand stowing in
mines, sound-proofing and as a mineral filler.
On the basis of mode of occurrence, shape and extent silicasand deposits in Rajasthan
may be classified into four categories i.e. :(i) With bedded sand stone / Quartzite-such deposits have greater lateral extension
eg. in Tertiary sandstone in Bikaner district; Alwar quarzite in Jhir; Manota,
Tunga etc. areas of Jaipur district; in lower Vindhyan in Kundi area of Kota
district etc.
(ii) patchy deposits-such deposits are small in size such as with Alwar quarzite in
Samod area of Jaipur district and Aravalli quarzite in Jawal area of Bhilwara
district. etc.
(iii) along faults and shear zones - such deposits have comparatively more depth
extension eg. in Vindhyan sandstone of Barodiya area in Bundi district &
(iv) colloidal silica pockets-residual product of weathering pulverised chert along
fault zone is called Tripoli, amorphus silica or colloidal silica eg. in Tirohan
breccia in Sapotra tehsil in distt. Karauli.
In India total estimated recoverable resources of quartz/ silicasand as on 1.4.95 is placed
at the order of 2,402 million tonnes of which proved reserves constitute (13.5%),
probable (25.5%), and possible (61.5%).
Out of the total resources of silica sand/ quartz in India, Rajasthan state contributes 12.9
million tonnes in proved category, 50.0 million tonnes in probable category and 67.59
million tonnes in possible category. Thus, contributing 130.5 million tonnes out of the
total 2,402 million tonnes reserve in India.
In the year 1998-99 total quartz production of the country was 2.17 lac tonnes, out of
which Rajasthan state produced 46.35 thousand tonnes.
Andhra Pradesh continued to be the principal producing State of quartz accounting for
46% of the total country's production, followed by Rajasthan 21 %, Tamil Nadu and
Gujarat 10% each, Bihar 7%, Karnataka 5%. The remaining 1 % was contributed by
Madhya Pradesh and Maharashtra.
In India major production of silica sand comes from Haryana, Maharashtra, Rajasthan,
Gujrat and Andhra Pradesh. In the year 1998-99 total 13.14 lac tonnes silica was
produced out of which, Haryana was leading with 3.96 lac tonnes subsequently Gujarat
produced 1.57 lac tonnes, Rajasthan 1.53 lac tonnes, Andhra Pradesh 1.48 lac tonnes,
Maharashtra 1.40 lac tonnes, Karnataka 0.88 lac tonne, Bihar 0.77 lac tonne, Kerala 0.72
lac tonne, Uttar Pradesh 0.65 lac tonnes and rest by Madhya Pradesh and Tamil Nadu.
OCCURRENCES IN RAJASTHAN
Rajasthan possesses good deposits of silica sand and quartz in the country. The quartzites
of Delhi Supergroup, Vindhyan Sandstone and Eocene beds in the state constitute
extensive sources of silica sand. The important deposits of silica sand are in Karauli,
Jaisalmer, Jaipur, Dausa, Chittaurgarh, Bundi, Bharatpur, Barmer, Alwar, Tonk and
Bikaner. There are 91 mining leases for silicasand in the state and about 191.66 thousand
tonnes was produced during the year 1999-2000.
Quartz occures in the form of veins or found associated with pegmatite intruding the
different geological horizons in the state. Other than the quartz, associated pegmatitic
minerals are feldspar, mica, tourmaline, garnet, beryl etc.
The commercial production of the quartz is mainly from pegmatite belt extending
roughly from mozambad in Jaipur district to Kankroli in Rajsamand district through
Ajmer, Bhilwara, Pali and Tonk districts.
This pegmatite belt is extending over a strike length of about 320 kms. having width of
about 96 km. Other than this a smaller pegmatite belt in Sikar district also imparts in the
production of quartz. Though major contribution of quartz production is from above
mentioned pegmatite belt, however vein quartz in the different geological horizons also
contributes towards the quartz resources of state.
There are 75 mining leases the quartz in the state and about 104.27 thousand tonnes was
produced during the year 1999-2000.
SILICA SAND
The district-wise description of the Silica sand deposits in Rajasthan is given below :
Jaipur district
Jhir: The Silica sand deposits in this belt are located about 30 km. east of Jaipur. The
belt extends from Gumanpura village in south to over a distance of about 22 kms. with a
width of 3 km. The state department has estimated about 8 million tonnes of resources in
this belt. Silica sand is also reported near Dhula Bumonpura, Kalola, Jamwa Ramgarh,
Bhuj, Khori, Nimora etc. The silica sand of Dhula & Gumanpura area analyses to 97.9%
SiO2 & 0.46% Fe2O3 where as in Khori area it has 96.88% Si2O2 & 0.39% of Fe203.
The average particle size of the sand in this belt is between 40 to 12 mesh (B. S. S.) i. e.
422 & 124 micron size.
Dausa district
Among non-metallic minerals quantitatively it is most prominent. The main localities of
silica sand are Kundal, Dantli, and Girota in teh. Dausa and Sikarai. The silica sand of
Kundal area is fine to medium grained and buff to white in colour. The SiO2 varies from
96-98.5%. in the Dantli area it is medium grained and reddish to white in colour with
SiO2 varying from 97.12% to 97.52%, Fe2O3 0.56%, Al2O3 0.32% to 0.62%..
In Girota also it is medium to coarse grained and pale red in colour. SiO2 varies from 97
to 98.5%. Other than these, minor occurrences, have also been reported near village
Chhaprala, Bhedoli in tehsil Dausa and Dendadera and Ranoh in tehsil Sikarai. As a
whole the silica sand available in the district is mostly ferruginous, hence, it is being used
in making coloured bottle glass and bangles, and sent to Firozabad, Agra etc. Most of the
silica sand areas are leased out.
'
Baran district
Silica sand or glass sand is found in Atru and Chhabra tehsil of Baran district.
Chhabra area: Silica sand occurrences have been noted from Hanuwant Khera,
Buakhera, Bhilwara, Bilwari Goriva etc. areas near Chhabra town. Preliminary
assessment carried out in Hanuwant Khera area by the Department of Mines and Geology
indicated silica sand deposits below shallow soil cover of 5 to 7 mts., mostly in the
agriculture fields. The crude sample indicated around 92% SiO2, 2 to 4% Al2O3 and
3.6% Fe2O3 . This silicasand may be suitable for making coloured glass, however this
needs detail laboratory testing and commercial vaibality is also to be established,
Atru (Kundi) area: Silica sand deposits are available around Kundi, Devpura area of
tehsil Atru. At places silica sand horizon is about 10 mts. thick occurring below Deccan
trap and is underlain by shales and siliceous limestone of Sirbhu shale formation.
Preliminary assessment indicated a reserve of 5.3 million tonnes of inferred category in
Dhologhati Ki Bar, Motipura, Malya, Balaji-Ki-Khati etc. The washed sample indicated
92 to 97% SiO2 with 0.21 to 0.58% Fe2O3. This deposits seems to be useful for
industrial use but can not be worked as most of the area falls in reserve forest.
Karauli district
The important silica sand deposits are located in Pator-Sapotara area extending from
Ganeshwari to Machh villages over a strike length of 1 km. in Sapotara and Karauli
tehsils. Besides this the other occurrences are near Jon, Ghat, Parli and Badrela in Toda
Bhim tehsil. In Sapotara and Karauli tehsils, silica sand is associated with Rewa sand
stone of Vindhyan Supergroup. It is white in colour and coarse grained and contain 92.26
to 95% silica. In Toda Bhim it occurs with Delhi Supergroup rocks.
Jaisalmer district
The Silica sand deposits are reported from Lathi, Devikot and Pithal in Jaisalmer district
with Lathi sandstone. It is pure white in colour and is spreaded over an area of about 20
sq. km. This sandstone has given silica sand due to weathring. In the sandstone quarries
workable Silica sand is exposed from 1.5 to 2.5 mt. depth. The analytical result reveals
SiO2 92 to 95%, AI2O3 1.2 to 3.99%, Fe2O3 0.63 to 1.29% and MgO and TiO2 as nil, It
could be utilised for the manufacture of Bottle Glass. About 14.4 M.T. reserves have
been assessed from this district.
Alwar district
Silica sand has been located in Narayani area. It is white in colour and fine grained.
Reserves of 64640 tonnes with 98% silica have been estimated in this area. Silica sand is
also found with gritty quartzite near Ghyaspur extending from Narayanpur to Bilia for
about 1 km. length. Silica sand has also been located near village Nathusar in about 400 x
80 mts. area where investigations have been done by the state department The silica sand
of Ghatra area was washed in the ceramic laboratory of the department. It was found that
by washing it can be improved from 91.9% silica to 98.36%. Iron could be reduced from
0.48% to 0.32% with sand recovery of 63%. The estimated reserves in this area are about
1.2 million tonnes. Small lenses of silica sand are also located near Sahroli, Chapra area.
Bharatpur district
Ferruginous silica sand is located near Jaggiwanpura village 35 kms. away from Bayana
railway station. The sand occurs as thin bands of friable quartzite within the massive
layers. Occurrences of silica sand are reported near village Doravli and in the north of
Karwan village. The sand is ferruginous. The silica sand is being mined from the mines
located in tehsil Bayana near village Acholi, Gudakhar, Navali, Agawali, Bajoli,
Talimpur & Jaswant Nagar. In Kaman tehsil it is being word near village Kalawata,
Nanerawas, Bol-kheda, Lahsar. In Weir tehsil it is being worked near village Mangren,
Gothra and Mansapura. This district is the second largest producer of Silica sand in the
the state next to Jaipur. On an average sand contain 96 to 97 % SiO2 and 0.15% to 0.5%
Fe2O3 and sand recovery is about 50%. The silica sand of Kaman area is ferruginous but
on beneficiation in the ceramic ore dressing laboratory of the state department, it was
upgraded to 98.2% SiO2 and 0.05% Fe2O3.
Bundi district
A good quality Silica sand deposit is located near Barodia in Bundi tehsil, 10 kms. from
Bundi. The deposit falls along the Great Boundary fault, which brings the Aravalli
against lower Bhander sandstone of Vindhyan Supergroup. The deposit is exposed in
about one km. long and 100 mts. wide belt. Silica sand contains as high as 99% silica
with 0.05 to 0.14% iron. Other areas where Silica Sand occur are Tikarda and Dhulsagar.
Tonk district
In the Nohla and Borthal areas of Niwai tehsil partly friable white quartzite are exposed.
Similarly in Bher and Sewad areas quartzite is found suitable for the production on Silica
sand on grinding. In Niwai reserves of friable white quartzite capable of yielding Silica
sand are estimated to be 36.8 million tonnes containing 97.6 to 98% SiOz and 0.2 to
0.52% FezO3.
Bikaner district
Mudh area of Bikaner district is well known for possessing qua]jty Silica sand deposit.
Chemical analysis of this Silica sand reveals 99.08 to 99.15% SiOz and 0.089% Fe2O3.
On the basis of exposed sections 1.4 million tonne reserves have been estimated in the
area. Other than this, Silica sand also occurs near Gurha, Jogira Talab and Kishanayet.
Nagaur district
Silica sand available in Khajawana area contains 91.22% SiO2, 2.88% Al2O3 and 0.32%
Fe2O3 with a recovery of 60%. 0.75 million tonnes reserves have been estimated in this
area.
Barmer district:
Around Deoka village in Sheo tehsil friable sandstone occurs below siliceous earth or
directly below 2 mts. thick desrtsand. The reserves of 0.3 million tonnes have been
estimated in the area. It is fine to medium grained containing some amount of clay and
minor ferruginous material.
QUARTZ
Ajmer district
Ajmer district is the major producer of good quality quartz in the state. In the district
quartz is being extracted from the zoned pegmatite. The important localities are Kalinjar,
Sandoliya, Kadampura, Gari-Arjunpura, Hanuwantiya,Mandoti, Kalat Khera, Vihar,
Ratanpura, Borara, Dolpura, Nagelev, Chavandiya, Satariya, Rasulpura, Nareli, Pagara,
Kora, Jawaja, Samod, Barol, Gudas, Rajgarh, Rawatmal, Bhimpur, Jorawarpura, Kharwa
etc.
Bhilwara district
After Ajmer, Bhilwara district is next for the production of quartz in the state. In this
district important localities are - Bikliya, Sulwara, Papdiya, Dholi, Ganeshpura, Devatri,
Jalampura, Doulatgarh, Rajaji Ka Khera, Takatpura, Ratanpura etc.
Pali district
Pali is also one of the major quartz producing district in the state important localities are
Kalaliya, Khiwal, Balupura, Lithriya, Kalasia etc.
Rajsamand district
In the Rajsamand district quartz has been produced mainly from Beri Ki Bhargal,
Devriya etc. areas.
Sikar district
A considerable contribution in the production of quartz is from Sikar district. Here also
quartz has mainly been produced from zoned pegmatite. The main locations are Kundala
Ki Dhani, Hasampur, Baguala, Jetpura, Sohanpura, Koliwali, Dokan, Dudhawas, Bagora
etc.
Tonk district
In this district also quartz has been mainly produced from zoned pegmatites from the
localities viz. Kabra, Sivas, Gangapura, Dantaji Ka Devra, Dhapola, Kantoli, Abisiya,
etc.
Jaipur district
In the Jaipur district quartz is being mined out from the localities viz. Ladera, Sakhun,
Kalyanpura, Bhonawas, Triveni etc.
Dausa district
Important quartz occurrences in the district are near villages Ramawas, Bhankri and
Dausa town itself. Good quality quartz is being produced from these locations.
JASPER
Jodhpur district is the sole produces of Jasper in the state as well as in the country. It has
been found to be a good abrasive and is used in emery and gritstone. Jasper occurs in the
form .of veins / pocket mainly near villages Mathania, Osian, Rundia, Sopra, Mogra,
Lawara, Tamtia etc.
QUARTZITE
Though at many places quartzite suitable as substitute for Silica sand and quartz is
available in the state, but systamatic studies have not carried out to identify such type of
quartzites. However in the Bher and Sewad areas of Tonk district and Pushkar area in
Ajmer district such type of quartzite have been identified. These are also reported in
Sikar, Jhunjunu & Udaipur districts.
INDUSTRIAL APPLICATION
The primary uses of silica is in the manufacture of all types of glass wares in ceramics
and ceramic glazes. Other Major uses are, in metallurgy (where silica is used as a
refractory, foundry sand, flux and as a source of silicon for the production of silicon
metal and ferrosilicon alloys); in the electronics; in the production of silicon carbide; in
the chemical industry and in the construction industry.
Silica sand is also used to maintain or increase the permiability of oil and gas bearing
formations; as a filler in acid-proof cement, putty, paint, expoxy and polyester, resins, in
horticulture, as a filtration medium; and for decorative purposes. Silica flour is used as
filler in plastic and rubber product.
The colloidal silica, the powdery chert, is chiefly used for buffing and subbing down auto
bodies and painted surfaces. It is also used in scouring and cleaning, in soaps and
detergents.
The major industrial applications and specifications of are as below:
Glass: Main use of silica minerals is in the manufacture of different type of glasses i.e.
glass container ware, bottles, amberglass containers, clear blint glass, vaccum bottles,
pressed, and other glass wares.
Foundry Industry: The main advantages of silica sand as a foundry or moulding sand is
that it has strength to resist the pressure from the molten metal being poured, it is
permeable enough to allow the vapours and gases to escape and its texture and
composition allow the mould to be smooth. Sand for foundry purposes should have well
developed grading, preferred shape and size, free from mica content and must have
enough alumina or clay to make it bind together.
Refractory Industry: Silica bricks are used in steel industry, as they can with-stand very
high temperatures, light in weight and do not shrink. For refractory, purity of raw
material i.e. the high silica content is essential with least possible A12O3. The presence
of A12O3 wers the refractoriness of silica.
Cement Industry: In cement industry silica sand and crushed sand stone are used as
addative to make for silica deficiencies in the raw mill. The sand of quartz, of light grey
or whitish variety and should be free from silt.
Fertilizer Industry: Silica sand is used in fertilizer industry as filler to balance the
fertilizer grades. There is no rigid specification for this industry. In some case even river
sand is used.
Chemical Industry: Quartz is used in the manufacture of phosphorous pentasulphide.
Silica sand free of iron is used in the manufacture of ultramarine blue.
Asbestos Products Industry: Silica powder is used as one of the constituents in the
manufacture of asbestos cement sheets/pipes.
Insecticide Industry: Silica sand is used as a carrier in the insecticide industry.
Specifications for this industry are not very rigid.
Electrode Industry: Silica sand or quartz powder is used as one of the components of
welding flux mixture in electrode industry. Sulphur should be 0.03% . (max.)
Coal Washery Industry: In coal washeries Silica sand is used as one of the ingredients
in the floatation process of coal. Sand having constant density of more than 2.64 is used.
Clay content is limited to 0.5%.
Paint Industry: Silica is used in paint because it offers acid resistance, scrubbing and
wear resistance. Lead content in SiO2 shall not exceed 0.03%.
Iron and Steel Industry: Quartzite is added to the blast furnace charge to correct silica
alumina ratio. Some steel plants also use banded heamatite quartzitein place of quartizitc.
Sodium & Potassium Silicate Industry: Sodium silicate is produce by fusing silica sand
or quartz powder and combined CaO /MgO content of 0.85%with sodium carbonate at
1200oC. to 1400oC. The ratio of NazCO3 to SiO2 can be varied to obtain of wide range
of products. Potassium silicate can be manufactured with silica minerals by using
potassium carbonate in place of sodium carbonate.
Ferro-Silicon Industry: Quartz free from phosphorus of arsenic is used in this industry.
The Al2O3 more than its prescribed limit affects reduction in the electric furnace. If
higher iron is present in quartz, then the fusion in the furnace takes place at lower
temperature and affects reduction process. Another important factor is that quartz should
have good thermal stability at 1200° C or more.
Rubber Industries: Silica sand and quartz is used as reinforcing filter to improve
physical properties of rubber. Generally, silica mineral with +98% SiO2 and less than
0.1% metallic impurities is preferred.
Water Filteration : Sand and gravel are usually used as filter media for filteration of
water. The ISI specificiation (IS: 8419 -1977) for this is given below:
Effective size: The particle diameter shall correspond to 10% finer on the grain size
curve. The uniformity coefficient ratio shall be D60/D10 where D 60 is the particle
diameter corresponding to 60% finer on the grain size curve and D10 is the particle
diameter corresponding to 10% finer on the grain size curve.
Filter Sand: Rounded grains are preferred to angular one for the removal of turbidity. It
shall consist of hard and durable grains of silica sand and shall have a specific gravity not
less than 2.5. The minimum SiO2 content shall be 90% and impurities like clay, silt, etc.
shall not exceed more than 5% by vlume. The acid soluble matter shall not be more than
5%. The loss on ignition shall not exceed O.7%.
Filter gravel: It shall consist of hard and preferably rounded stones with an average
specific gravity of not less than 2.5. It shall be free from clay, sand, loam and organic
impurities. It shall contain not more than 2% by mass of thin, flat or elongated pieces
determined by hand picking. The acid solubility for gravel sizes 10mm or larger should
not exceed 10% and for sizes smaller than 10mm it should be less than 5%. Gravel
should be free from excessive amount of limestone and shell.
Sand-Lime Bricks Industry: Large quantitites of silica sand are used making sand -lime
building bricks. For this purpose sand may contain upto 2% of clay but it should not at
any rate exceed 5%. It should be evenly graded. At least 10% should pass 150 mesh and
all should pass 20 mesh. It should be sharp and angular, reasonably clean and free from
organic matter.
Plastering mortars: Natural and coarse sands are used in mortars for internal wall and
ceiling plastering and external plastering using mixes of lime, cement, gypsum and sand.
The ISI specifications (IS: 15421977) for sand plaster is as under:
The sand shall be hard, durable, clean and free from disoriented coating and organic
matter. It shall not contain any appreciable amount of clay balls. Clay and dust-contents
should not exceed 5% by weight. The sand should not contain impurities such as iron
pyrites, alkalies, salts, coal, mica, shell, organic impurities, etc. These impurities adversly
affect the hardening, the strength, the durability and the appearance of the plaster.
Ceramics: In ceramics usually quartz is used. However, high purity silica sand is
sometimes used for the manufacture of porcelain, stoneware, earthenware etc.
Silica as a flux: Sandstone, silica sand and quartzite are often used as fluxes in base
metal smelting where iron and basic oxides are slagged as silicates. The free silica
content-the active slagging agent-should be hgih, although minor amounts of iron and
alumina can be tolerated. Silica fluxes are also used in the production of elemental
phosphorus in electric furnaces.
Electronics: Single silicon crystal made by seeding molten silicon with a small silicon
crystal in a very high grade quartz crucible, are widely used in the electronics industry.
Germanium was first used as a current rectifier but was replaced by silicon which could
operate up to 180° C compared with germanium's maximum operating temperature of
80°C. Silicon is used in the non-ferrous metal industry,
particularly in the production of aluminium and copper alloys. It is also used in the
production of silicon cemets (ceramic particles bonded with silicon to make them
resistant to oxidation).
Abrasives : Silica's moderate hardness of 7 on the Moh's scale is utilised extensively in
the abrasive industry (the hardness is only moderate when it is compared with diamond at
10, silicon carbide at 9.5 to 9.6, emery at 7 to 9, and garnet at 6.5 to 8.5). Silica is used in
preference to these harder materials because of its low cost and wide spread availability.
It is used extensively as a coated abrasive (sand paper) which in turn is used in general
repair and maintainance, in finishing leather and electrical equipments.
Another abrasive use of silica sand is in sand blasting whereby sand is blown under
pressure, usually in the presence of water to suppress the dust, against the
material to be cleaned or polished. Although angular sand promote better cutting action,
this advantage is invalidated by an increase in the loss of fines (the sand is always
recovered for re-use). Although the chemical composition of the sand is relatively
unimportant, size frequency distribution and the absence of clay or any other clogging
materials are of the utmost importance. Because of the dust and silicosis problem
associated with sand blasting, other materials, particularly garnet, are now being used as
substitutes. In addition, silica sand used for glass grinding is on the decline because the
float glass process eliminates the need to polish the flat glass. To round off, flint pebbles
are often used as the grinding medium in ball mills, and quartzite blocks are used in the
lining of tube mills.