Non-silicate
Crystal system: cubic
Colour in hand specimen: extremely variable: colourless, white, yellow, green, blue and purple most common
Cleavage: perfect octahedral, up to four visible at one time, breaks into dipyramids
Hardness: 4
Colour in plane polarised light: colourless, pale green or pale violet
Pleochroism: none
Relief: low
M560 Fluorite
Derbyshire
Cubic fluorite crystals
Generally very variable; in this case white to purple
Glassy lustre
Hardness 4
Octahedral cleavage
Non-silicate
Crystal system: cubic
Colour in hand specimen: extremely variable: colourless, white, yellow, green, blue and purple most common
Cleavage: perfect octahedral, up to four visible at one time, breaks into dipyramids
Hardness: 4
Colour in plane polarised light: colourless, pale green or pale violet
Pleochroism: none
Relief: low
M560 Fluorite
Derbyshire
Cubic fluorite crystals
Generally very variable; in this case white to purple
Glassy lustre
Hardness 4
Octahedral cleavage
Non-silicate
Crystal system: hexagonal (-)
Colour in hand specimen: green, white, yellow, blue brown etc.
Hardness: 5
Colour in plane polarised light: generally colourless
Pleochroism: weak to moderate in coloured varieties
Relief: moderate
Birefrinence: 0.001-0.007; first order greys
Extinction: straight
Form: commonly hexagonal in cross-section
Non-silicate
Crystal system: hexagonal (-)
Colour in hand specimen: green, white, yellow, blue brown etc.
Hardness: 5
Colour in plane polarised light: generally colourless
Pleochroism: weak to moderate in coloured varieties
Relief: moderate
Birefrinence: 0.001-0.007; first order greys
Extinction: straight
Form: commonly hexagonal in cross-section