Browse Items (264 total)

Formula Fe2O3 Structure Non-silicate Crystal System Crystal system: trigonal (-) Physical Properties Colour in hand specimen: black, steel-grey and bright to dull red Streak: cherry-red Cleavage: none Hardness: 5-6 Optical…

Formula SiO2 Structure Framework silicate Crystal System Crystal system: trigonal (+) Physical Properties Colour in hand specimen: colourless Lustre: vitreous Pleochroism: none Cleavage: none Hardness: 7 Optical Properties Colour in…

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 (K,Na)[AlSi3O8] Structure Framework silicate Crystal System Crystal system: monoclinic (-) or triclinic (+) (-) Physical Properties Colour in hand specimen: white or pink Cleavage: two at 90° Hardness: 6-6.5 Optical…

Formula Mg3[Si2O5](OH)4 Structure Sheet silicate Crystal System Crystal system: monoclinic or orthorhombic (-) Optical Properties Serpentine is commonly very fine-grained. It can be recognised by its textural association with olivine…

Formula (Mg,Fe2+,Fe3+,Mn,Al)12[(Si,Al)8O20](OH)16 Structure Sheet silicate Crystal System Crystal system: monoclinic (+) (-) Physical Properties Colour in hand specimen: green Cleavage: one, good Hardness: 2-3 Optical…

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,K)0-1Ca2(Mg,Fe2+,Fe3+,Al)5Si6-7.5Al2-0.5O22(OH)2 Structure Chain silicate Crystal System Crystal system: monoclinic (+) (-) Physical Properties Colour in hand specimen: black Cleavage: two at ~56° Hardness: 5-6 Optical…

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…