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KOTA STONE MINING – ENVIRONMENTAL ISSUES

A. Hussain

Mining industry is one of the most important and old industry supporting the

country’s economy. The present trend is to opt for opencast mining in place of under

ground mining. At present country’s 25 lakh hectare area is under mining lease

conditions, out of which ninety percent area is subject to opencast mining techniques.

In general, all the mines affect their surrounding environment to a little or more

extent, but opencast mining in particular lead to complex nature of environmental

problems. In these circumstances it became imperative to mine planners and operators

to plan and execute mining programmes in such fitting manner so that the impact of

mining on the local environment is brought to a negligible state or preferably to a

zero level. This requires a careful planning as well as more attentive work execution

on day to day basis. Impact on the local environment is more aggravated and complex

in case of small mines exploiting minor minerals such as marble, granite Kota Stone,

sandstone and other type of building stone quarries.

Kota and Jhalawar districts of Rajasthan have been subsisted with about 100

million tonnes of splitable type of decorative grade flooring limestone, better known

as Kota stone. A typical chemical composition of Kota stone is given in table-A

Table – A

Kota Stone Chemical Composition

S. No. Chemical Constituent Percentage (weight)

1 Calcium Oxide 37.30

2 Magnesium Oxide 4.13

3 Sodium Oxide 1.21

4. Potassium Oxide 0.40

5. Aluminium Tri Oxide 1.37

6. Ferrous Oxide 0.86

7. Titanium Di Oxide 0.05

8. Silica 24.90

9. Loss on Ignition 32.94

These deposits are part of vindhyan range of sedimentary rocks, overlain by sand

stone cappings. In general Kota stone mining areas are free from sand stone coverings

and the entire profile consists of different grades of lime stone beds. The floor grade

limestone is available in a variety of different colors including blue, green, brown or

spotted type. Color pattern is governed by the chemical composition where main

players are iron, Titanium and Aluminium.

Kota stone formations outcrop in varieties of colours, predominantly blue, green,

brown or their combinations etc. At place calcitic veins are are distinctly criss-

crossing the deposits. Soil subsoil and non splittable lime stone layers are overlying

these deposits.

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The kota stone deposits are located between latitudes N 24o 32’ and N 24

o 48’ and

longitudes E 75o 50’ and E 76

o 05’ and it is covered on topo sheet No 45/D/13.

45/D/14, 54 D/1 and 54 D/2.

The various Kota Stone laminations are nomenclatured locally in an uniform

language. Geologically Speaking, Kota Stone is part of Semi Series of lower

Vindhyan group. The local nomenclature are well understood and prevailing from the

inception of the mining in this area. The regional stratigraphic sequence of the deposit

is given in table-B

Table-B

Regional Stratigraphic Sequence

(A) Upper Vindhyan

1. Bhander Series

2. Rewa Series

3. Kaimur Series

4. Semi Series

(B) Lower Vindhyan

1. Suket Shales

2. Nimbahera Lim Stone

3. Jhalrapatan Sand Stone

The Kota Stone deposits are spreaded over 150 square kms area and the total probable

reserves up to minable limits is about 100 million tones. A fair area-wise distribution is

given in Table-C

Table-C

Area wise Kota Stone Reserves

S/No Area Minable Reserves in Million Tonnes

1. Chechat 30.00

2. Pipa Kheri- Nayagaon Belt 2.00

3. Suket- Atraliya

Sahravada- Kukra Belt 4.00

4. Suket- Dingsi . 10.00

. Pampakheri, Atraliya

Dhabadeh, Belt

5. Dhabadeh- Teliya Kheri 10.00

Sahravada, Kukada, Belt

6. Manpura- Dhani 4.00

Extending Jhalawar district

7. Jagankheri – Kumbhkot 30.00

Laxmipura- Satalkheri

Pipakheri, Belt

8. Julmi- Belt 5.00

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9. Atraliya Deposit 5.00

Total 100.00

The workable lime stone beds ameanable to splitting are located at a depth range

from 15.0 mtrs to 25.0 mtrs from the surtace and form part of anticlinal- syniclinal type

of sedimentary laminated structures.

Strike and Dip of the deposit is primarily location specific, but generally the

deposit dip at 7.5 percent away from the anticlinal – synclinal common axis. The

limestone bed is divided into five prominent sacks which are separated from each other

by clay partings. Thickness of Laminations in each sacks increases with depth and texture

also improves. However the lamination thickness and texture improves with higher Silica

fractions in the sacks, as given in table-D.

Table-D.

Silica Percentage in Different Sacks

S. No. Sack Average Silica

Percentage

Quality Considerations

1. Top Kota Stone

Sack

18.00 Thin laminations with rough

texture

2. Middle Sack 20-22 Aggregated lamination

thickness increases better

texture

3. Third Sack 22-24 Product size have larger portion

of thick laminations and very

good texture.

4. Fourth Sack 24-27 Thick laminations and very

good texture

Stratigraphic profile also varies from place to place and can be divided into three

categories depending upon the type of waste material overlying the workable deposits,

viz.

1. Overburden Comprising soil, sub-soil and mixed calcareous - like chechat area.

2. Overburden Comprising soil, sub-soil and Basalt rock-like Pipakheri, Zulmi area.

3. Overburden Comprising soil; sub-soil to a large extent underlain by a narrow

band of calcareous rocks-like Jhalwar district deposits.

The stratigrapic rock profile of all three deposits are shown in Table-E.

Table-E

Stratigraphic Rock Profile

S. No. Rock Thickness in Mtrs.

Chechat Group Pipakheri

Group

Jhalawar

District Mines

1. Top Soil/Sub Soil 0.00 – 2.50 0.00 – 1.50 10.00 – 11.00

2. Overburden Comprising

mixed calcareous Rocks

10.00 – 25.00 - 3.00 – 4.00

3. Basalt - 10.00 – 12.00 Nil

4. Top Sack 4.00 – 5.00 4.00 – 5.00 -

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5. Middle Sack 2.50 – 3.00 2.50 – 3.00 -

6. Third Sack 3.00 – 4.00 3.00 – 4.00 3.00 – 4.00

7. Fourth Sack 1.25 – 2.00 1.25 – 2.00 1.25 – 2.00

Semi mechanized mining method is usually adopted, where the overlying waste

material is removed with the help of hydranlic excavators having bucket size 0.5 to 0.9

cu. meter and tippers of 10.0 to 15.0 mt bucket capacity. Hard overburden is drilled with

125 mm size water-hole drilling portable rigs. The drilling pattern in the soft rocks is

maintained at 4.0 x 4.5 mtrs, while in Basalt it is narrowed down to 3.0 x 3.0 mtrs

Mixture of conventional cartridged explosives and ANFO is used for blasting. In Basalt

the charging factor is kept at the rate of 1.25 kg per foot of drilled hole length, while in

other cases it is 0.8 kg/foot of drilled length of hole. Radiat blasting techniques is used in

the sensitive areas, while at other places 17 ms relays are used to provide relief between

detonating rows.

The workable tables are given 150 mm to 450 mm deep cut channels at an

interval of 0.6 mtrs distance with the help of electric motor driven Jhirri machines. Semi-

Skilled artisans, cut and size different length of slabes from these bays and stack at

designated places, from where the slabes are loaded into trucks and transported to sales

stock, maintained at quarry top. This entire operation is manually operated.

A general statement of Kota Stone production from 1996-97 to 2011-12 is given

in Table-F

Table-F

Year wise Kota Stone Production (Figures are approximate)

S. No. Year MT.

1 1996 - 97 10.00

2 1997 - 98 21.00

3 1998-99 22.00

4 1999 - 2000 20.00

5 2000-01 21.00

6 2001 – 02 22.00

7 2002-03 23.00

8 2003 – 04 30.00

9 2004-05 28.00

10 2005 – 06 35.00

11 2006-07 30.00

12 2007 – 08 40.00

13 2008 – 09 45.00

14 2009-10 40.00

15 2010 – 11 50.00

16 2011 - 12 55.00

The average yield of acceptable quality of Kota Stone per hectare land area is

about 1.00 lakh M.T, and with the current trend of yearly production level, 55.0 to 60.0

hectare land is brought under stone mining each year. In all cases this land belongs to

farming sector and is completely degraded as far as agriculture is concerned. In a rough

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estimate, till date almost 900 hectare prime agriculture land has been lost to Kota Stone

mining alone in Kota and Jhalawar districts. Damage to land surface from sand stone

mining is not included in this assessment.

In addition to the environmental problem cropping up due to permanent loss of

prime agricultural land, there is one more dimension to this activity i.e. formation of

waste dumps over agricultural land. Most of the mining leases are of 4.0 Ha to 25.0 Ha

size areas, where side by side pit reclamation is not possible. The angle of repose of the

blasted overburden is almost 380, which requires a sizable space in the operative sections,

apart from productive platforms, facility recess, and water sink and other utility Space.

As a result, large quantity of blasted wastes are dumped over prime agricultural tracts,

specially purchased for making these waste Dumps. The quantum of problem can be

understood by the figure that 2.5 cum waste has to be stripped off and dumped in the

dump-yards for each metric tonne of Kota Stone production. Capacity of the dump-yards

retaining waste material depends upon many factors such as size, shape, angle of repose

etc, but on an average 1.0 Hq area dump-yard may hold about 1.75 lakh m3 waste

material taking into account angle of repose, optimum square shape and space for haul

roads and benches etc.

The present trend of production level is likely to generate about 138 lakh m3 of

waste material every year. Presently only 35 percent of this bulk quantity is filled back in

the mined out areas, leaving behind 90.00 lakh m3 waste dumped over prime agricultural

land, requiring 45.0 to 50.0 hectare fresh land for dumping waste generated in a year. As

per our estimates around 1800 lakh m3 waste material is dumped in random formations

covering about 900 to 1000 hectare area.

The third dimension to this problem is of the disposal of the fine slurry released

from the cutting polishing industries. Every year about 2.5 to 3.0 lakh mt of stone polish

is discharged into local convenient places. This affects about 5 to 10 hectares land every

year.

In total both Kota and Jhalawar district are loosing about 120-150 Hectare prime

agriculture land every for facilitating Kota Stone mining, which is quite alarming.

In addition to this one more point needs immediate attention. Kota Stone is a

localized non-renewal natural resource and its limited reserves may not last another

fifteen years with the current policy of liberalized lease sanctioning process and increased

production level. This aspect needs introspection from the point of sustainable growth

and regulation.

The mining in these districts is loosing valuable top - soil at the rate of 8.0 to 8.50

cu.mtrs per year, which is another loss to eco-system.

To overcome the environmental problems as highlighted above, following

measures are recommended.

1. Fresh mining leases should be considered exclusively on the land presently

occupied by the old waste dumps.

2. Mine-owners should be pressed to dumps their waste generations into nearby old

abandoned quarries.

3. The case agreements should have special provisions to force con-current refill after

an initial grace period to facilitate development and space for such refills.

4. Cutting polishing industries should be forced to dump their slurry into old mined

out areas or in the active dumps. Any violation should be penalized.

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5. Top soil should be mined out separately and conserved for reclamation purposes.

(A.HUSSAIN)