Kaolinite
Sheet Silicates
triclinic/monoclinic (-)
Relief - low
Colour - colourless - brown
RI - 1.553-1.570
Birefringence ~ 0.006
Interference colours - 1st order greys
Comments - very fine grained crystals
Patches in topaz altered to kaolinite
XPL
Megilligar Rocks, Cornwall, UK
Patches in topaz altered to kaolinite
XPL
Megilligar Rocks, Cornwall, UK