Browse Items (6 total)

Formula Na[AlSi3O8] – Ca[Al2Si2O8] Structure Framework silicate Crystal System Crystal system: triclinic (+) (-) Physical Properties Colour in hand specimen: white Cleavage: two at 90° Hardness: 6-6.5 Optical Properties Colour in…

Formula (Ca,Mg,Fe2+,Fe3+,Ti,Al)2[(Si,Al)2O6] Structure Chain silicate Crystal System Crystal system: monoclinic (+) Physical Properties Colour in hand specimen: black Cleavage: two at 90° Hardness: 5.5-6 Optical Properties Colour in…

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 (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 Fine-grained, greenish black rock comprising dark and white minerals. Contains amygdales, mostly white, though some have black cores. Thin-section Fine-grained plagioclase laths and irregular clinopyroxene…

Hand Specimen Very dark grey, coarse-grained rock, typical grain size 1-2 mm. Main mineral phases are black clinopyroxene, greenish olivine and pale grey feldspar. The rock is cross-cut by a small number of hairline white…