Physically, these are Metamorphic-Argillaceous rocks, which has developed a well-marked splittable cleavages with or without developed recrystallization & spots/knots of minerals like garnet, pyrite, andulasite, etc. They are normally fine to medium grained, moderately hard & compact, less homogeneous with varying textures & shades. It has an ability to split into thin layers along the plane of cleavages due to flattened & elongated minerals along the plane of cleavage.
|Hardness||3.0 to 4.0 on Moh's scale|
|Density||2.6 to 2.8 Kg/cm3|
|Modulus of Rupture||22 to 34 N/mm2|
|Compressive Strength||24 to 36 N/mm2|
|Specific Gravity||2.65 to 2.80|
|Porosity||Low to very low|
|Water Absorption||1.5 to 2%|
|Corrodibility||0.4 to 0.7%|
Chemically, they are Multi-Mineral, metamorphic argilaceous rocks made of an aggregate of minerals and colloidal substances. Essentially mineral composition includes quartz, mica, chlorite, sericite & oxides of iron with occasional spots/knots of minerals like garnet, pyrite, andulasite, etc.
|Alumina (Al2O3)||15 to 20%|
|Soda (Na2O) & Potash (K2O):||2-4%|
|Loss On Ignition (LOI)||3-4%|