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Pyrophyllite

Pyrophyllite is a secondary mineral of composition Al₂O₃ 4 SiO₂ H₂O. In appearance it looks like talc and in physical properties also it is identical to talc but in chemical composition it differs form it. Talc is a hydrous magnesium silicate while pyrophyllite is hydrous aluminum silicate.

Pyrophyllite finds the same use as talc. It is used in insecticide, refractory bricks and industries. It is regarded to have better refractoriness than steatite.

There is no BIS specification for pyrophyllite for its use in any industry. However, specifications quoted by major consuming industries is as follows:

1.Refractory

Chemical

28% Al₂O₃ to 31% Al₂O₃

3 - 4% Alkali

28 to 30% Orton PCE.

The sub-committee on refractory Raw Materials of the DGTD for refractories has stipulated the two grades mentioned below:

Refractory	Grade-I	Grade-II
Al₂O₃	38% min.	28% min.
SiO₂	60% max.	60% max.
Alkalis	1% max.	1% max.
PCE	30% min.	28% min.

1. Ceramic Industry:

Physical

Residue below

150 U sieve

- 95%

Chemical

SiO₂ 64 ± 2%

Al₂O₃ - 28 ± 2%

Fe₂O₃ - Less than 1%

TiO₂ – Less than 0.2%

K NaO – Less than 1%

CaO - Less than 0.5%

MgO – Less than 0.5%

LOI – 4.5 ± 1%

2. Insecticide Industry:

There is no separate specification available for use of pyrophyllite in insecticide industry. However, the specifications for insecticide industry as available for talc/steatite can also be applicable to this, which is as below:

L. O. I.	7% max.
Matter soluble in HCL	3% max.
Fe₂O₃	1.5 max.

Pyrophyllite has not been included in the list of minerals for the preparation of mineral inventory. However, the known reserves are not at present classified according to the end use.

Industry:

Refractory

Al₂O₃

SiO₂

Alkalies

PCE (Orton cone.)

28% min.

60% max.

1% max.

28% min.

Ceramic

Al₂O₃

SiO₂

Fe₂O₃

TiO₂

CaO

MgO

28 ± 2%

64 ± 2%

Less than 1%

Less than 0.2%

Less than 0.5%

Insecticide

L. O. I.

Matter soluble in HCL

Fe₂O₃

7% max.

3% max.

1.5% max.

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