Anhydrite (orthorhombic) Ca[SO4]

|
Colour: colourless Pleochroism: non pleochroic Habit: tabular, prismatic or square shaped cross section, grained aggregates Relief: positive Cleavage, fracture: perfect (100) and (010), good (001)
|

|
Isotropic or anisotropic: anisotropic Extinction: straight Interference colours: 2nd/3rd order
|
Gypsum (monoclinic) Ca[SO4] x 2H2O

|
Colour: colourless Pleochroism: non pleochroic Habit: massive, tabular crystals Relief: low negative Cleavage, fracture: perfect (010) Twinning: common (110) called swallow-tail
|

|
Isotropic or anisotropic: anisotropic Extinction: straight Interference colours: 1st order, grey, yellow
|
Last modified: Monday, 3 April 2017, 10:51 AM