Browse Items (264 total)

Formula (Mg,Fe)2Si2O6 Structure Chain silicate Crystal System Crystal system: orthorhombic (+) (-) Physical Properties Colour in hand specimen: black Cleavage: two at 90° Hardness: 5-6 Optical Properties Colour in plane polarised…

Formula (Na,Ca)(Mg,Fe,Mn,Li,Al)3(Al,Mg,Fe3+)6[Si6O18](BO3)3(O,OH)3(OH,F) Structure Ring silicate Crystal System Crystal system: trigonal (-) Physical Properties Colour in hand specimen: blackHardness: 7 Optical Properties Colour in…

Formula Ca2Al2O∙(Al,Fe3+)OH[Si2O7][SiO4] Structure Orthosilicate Crystal System Crystal system: monoclinic (-) Physical Properties Colour in hand specimen: greenCleavage: one, perfectHardness: 6 Optical Properties Colour in plane…

Formula (Mg,Fe,Ca)3Al2Si3O12 Structure Orthosilicate Crystal System Crystal system: cubic Physical Properties Colour in hand specimen: typically redCleavage: noneHardness: 6-7.5 Optical Properties Colour in plane polarised…

Formula CaTi[SiO4](O, OH, F) Structure Orthosilicate Crystal System Crystal system: monoclinic (+) Physical Properties Colour in hand specimen: colourless, yellow, green, brown or blackCleavage: one, goodHardness: 5 Optical…

Formula Zr[SiO4] Structure Orthosilicate Crystal System Crystal system: tetragonal (+) Physical Properties Colour in hand specimen: reddish brown, yellow, grey, green or colourlessHardness: 7.5 Optical Properties Colour in…

Formula (Mg,Fe)2[SiO4] Structure Orthosilicate Crystal System Crystal system: orthorhombic (+) (-) Physical Properties Colour in hand specimen: pale greenCleavage: none, instead it has characteristic curving cracksHardness: 7 Optical…

Hand Specimen Buff coloured rock.Almost pure quartz, which has been very well recrystallised.Faint banding could be original bedding. Thin-section Fine to medium grained recrystallised quartz with sutured contacts. Rock History The sutured…

Hand Specimen Almost entirely made up of fine sand sized quartz grains. Does not fizz with acid, so no carbonate present. Clean white rock, apart from pink-brown weathering. Dark carbonaceous marks are plant roots. Thin-section Subangular…

Hand Specimen Strongly developed planar fabric made up of platy biotite mica and muscovite mica grains and lenses of quartz grains. Fabric wraps around large, euhedral garnets, typically ~2mm across. Quartz, the most soluble mineral, has…