Browse Items (6 total)

Formula K2(Mg,Fe2+)6-4(Fe3+,Al,Ti)0-2[Si6-5Al2-3O20](OH,F)4 Structure Sheet silicate Crystal System Crystal system: monoclinic (-) Physical Properties Colour in hand specimen: brown or black Cleavage: one, good Hardness: 2-3 Optical…

Formula K2Al4[Si6Al2O20](OH,F)4 Structure Sheet silicate Crystal System Crystal system: monoclinic (-) Physical Properties Colour in hand specimen: colourless Cleavage: one, good Hardness: 2.5-3 Optical Properties Colour in plane…

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 (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…

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…

Hand Specimen Very fine-grained rock with a prominent, well-developed cleavage. The dark red-purple colour is due to iron-staining. The light green smudge is a reduction spot. Thin-section Mud size grains.Mainly indistinguishable clay…