Framework silicate
Crystal system: trigonal (+)
Colour in hand specimen: colourless
Lustre: vitreous
Pleochroism: none
Cleavage: none
Hardness: 7
Colour in plane polarised light: colourless
Pleochroism: none
Relief: low
Birefringence: 0.009; 1st order grey
M410 Quartz
Characteristic prismatic crystal form: hexagonal cross-section, needle-like; hexagonal prism surmounted by a hexagonal pyramid
Colourless, transparent, milky in places
M411 Quartz
Madagascar
Colourless, transparent quartz fragment, milky due to cracks and crystal boundaries
Vitreous lustre, conchoidal fracture, no cleavage
M412 Quartz (with galena and pyrite)
North Wales
A mass of small hexagonal quartz prisms, with galena, pyrite and zinc blende.
Transparent, white to light grey
Galena: purple-black, shiny, platy habit, metallic
Pyrite: metallic lustre, gold colour, cubic habit, “Fools’ gold”
Framework silicate
Crystal system: trigonal (+)
Colour in hand specimen: colourless
Lustre: vitreous
Pleochroism: none
Cleavage: none
Hardness: 7
Colour in plane polarised light: colourless
Pleochroism: none
Relief: low
Birefringence: 0.009; 1st order grey
M410 Quartz
Characteristic prismatic crystal form: hexagonal cross-section, needle-like; hexagonal prism surmounted by a hexagonal pyramid
Colourless, transparent, milky in places
M411 Quartz
Madagascar
Colourless, transparent quartz fragment, milky due to cracks and crystal boundaries
Vitreous lustre, conchoidal fracture, no cleavage
M412 Quartz (with galena and pyrite)
North Wales
A mass of small hexagonal quartz prisms, with galena, pyrite and zinc blende.
Transparent, white to light grey
Galena: purple-black, shiny, platy habit, metallic
Pyrite: metallic lustre, gold colour, cubic habit, “Fools’ gold”