Slate is a fine-grained, foliated, homogeneous, metamorphic rock. Slate can be made into roofing slates, also called roofing shingles. Slate tiles are often used for interior and exterior flooring or wall cladding. Tiles are installed and set on mortar and grouted along the edges. Sealants are often used on tiles to improve durability and appearance, increase stain resistance, reduce efflorescence, and increase or reduce surface smoothness.

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%
Weather Impact Resistant
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.

SiO2 55-65%
Iron (Fe2O3) 4%-8%
Alumina (Al2O3) 15 to 20%
Soda (Na2O) & Potash (K2O): 2-4%
Lime (CaO) 0.5-1%
Magnesia (MgO) 0.5-3%
TiO2 0.4-0.5%
Loss On Ignition (LOI) 3-4%