Fluorspar
Fluorspar or Fluorite is a common name given to a mineral having chemical composition of calcium fluoride (CaF2)

The utility of fluorite can be described broadly under four heads (I) as fluxing agent in the iron and steel industry; ferro-alloys; foundries and in the manufacturing of electrodes; (ii) as vitrifying and specifying agent in glass industry, and (iii) as an additive to cryolite batch in aluminum metallurgy, and (iv) as a source of fluorine in chemicals, synthetic cryolite for use in the aluminum industry, refrigerant.

Fluorspar is mined and marked usually after beneficiation in three grades: (I) metallurgical (ii) ceramic and (iii) acid.

The BIS (IS: 4574 1981) has prescribed the following specifications for metallurgical grade fluorspar:

Constituents

Requirement Percentage
Grade-I             Grade-II           Grade - II
For Aluminum               For Steel Industry

Calcium Fluoride (CaF2) (min.)

97

85

80

Silica (SiO2) (max.)

1

6

8

Effective Cal. Fluorite (CaF2) min.

-

70

60

Calcium Carbonate (CaCO3) max.

1

3

3

Mixed Oxide (R2O3)

1.5

3.5

3.5

Sulphur (max.)

0.1

0.3

0.3

Lead (max.)     

-

0.3

0.3

Note: The % "effective" percentage is calculated by multiplying the silica percentage in the analysis by 2.5 and subtracting this number from the CaF2 percentage in the analysis.

The GMDC markets metallurgical grade fluoride having the composition CaF2 85% (min.), CaCO3 3% (max.), SiO2 4.5% (max.) Fe2O3 + Al2O3 3.50% (max.), P2O5 1% (max.) BaSO4 0.50% (max.).

According to GMDC this grade of concentrate has been widely accepted by the industry.

As per the Rajasthan State Mineral Development Corporation, fluorite to be use as a flux for making special steel would have 80-85% CaF2 and in ordinary steel it would have 70-75% CaF2

CHEMICAL GRADE:

Constituents           

Percentage

Free Moisture

10

CaF2 min. percent by mass

96

SiO2 max.

1

Calcium (as CaCO3) max. % by mass

1.2

Sulphur (as S) max. by mass

0.08

Barium (as BaSO4) by mass

0.05

Phosphorous (as (P2O5) max. by mass

0.20

Mixed Oxide (as (R2O3) max. by mass

1.5

Organic matter

0.25

Chlorite to pas the test

 

Beryllium to pas the test

 

Size      (1)        Retained on 500-micron sieve nil mass.

             (2)        Retained on 212-micron sieve.

             (3)        Retained on 75-micron sieve.

 

10

25 max.

 The GMDC markets the following two acid grades:

 

Acid Grade 'A'

Acid Grade 'B'

CaF2

96% and above

93% to 95%

CaF2

96% (min.)

1.50% (max.)

SiO2

1.0% (max.)

1.5% (max.)

Fe2O3 + AI2O3

1.5% (max.)

1.6% (max.)

P2O5

0.20% (max.)

0.60% (max.)

BaSO4

0.20% (max.)

0.30% (max.)

According to the GMDC, to meet the specifications set up by the aluminum industries for manufacturing aluminum fluoride, acid grade 'A' has been used all along in a suitable blend with the imparted concentrates. However, acid grade 'A' as well as acid grade 'B' as mentioned above have been fully accepted by other chemical industries such as synthetic cryolite, refrigerant gases, stainless steel etc.

According to RSMDC, fluorite would have 90 - 95% CaF2 and above for chemical industries for making acids, synthetic cryolite and aluminum fluoride.

Ceramic Grade: - There is no BIS specification for this grade. The specifications prescribed by user industries is that fluorspar should contain CaF2 - 95% (min.), SiO2 2.5% (max.), Fe2O3 0.12% (max.) while CaCO3 be 1% (max.)

Glass: - BIS has not prescribed any specification for this industry. However, based on user industries CaF2 should be (a) from 90 - 98% pure (b) 65 to 80% with size 75 to 150 mesh in most cases.

Mill Head Grade: - In order to produce the grade reported by GMDC, it is necessary to have following head grade for the plant;

 Mineral

Constituent

Percent

CaF2

24% 5%

CaCO3

4.0% 1%

P2O5

1.2% 5%

SiO2

60% 5%

 The entire reserves of fluorspar were placed under " unclassified grade" in the inventory as on 1.1.80. However based on the experience regarding mill - feed grade in the benefaction plants in the country and also based on the current market demand of hand sorted graded of fluorspar, the current market demand of hand sorted graded of fluorspar, the production from different mines have been classified into following grades and their ratios in the ROM ore have been applied to reserves to arrive at grade - wise reserves:

 (i)        70 - 80 CaF2

(ii)        60 - 70% CaF2

(iii)       50 - 60% CaF2

(iv)       30 - 40% CaF2

Fluorite is by and large beneficiated before it is used in various industries, because the deposits are low-grade. Also, the ore exhibits a very short-range variability in respect of its grade and in other parameters. Therefore, end use classification of reserves is not possible. The reserves may be estimated on an average grade basis as given below: -

Reserves:

CaF2 24% (min.)

P2O5 1.2% (max.)

CaCO3 4.5% (max.)

SiO2 65% (max.)

CaF2 below 24%

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