Olivine is the mineral group crystallizes first during the magma cooling as per Bowen reaction series. It has the general formula X2SiO4 , where X = Fe, Mg, Mn and Ca. with charge of +2. Structure – Olivine solid solution – Because there is similar ionic radius and ionic charge of cations. olivines make a […]
Common minerals : Andalusite, Sillimanite, Olivine, Enstatite etc. Classes of the System Unit forms of Normal class : Form No. of faces Miller Indices Basal Pinacoid 2 001 front Pinacoid‘a’ PinacoidMacro Pinacoid 2 100 Side Pinacoid‘b’ Pinacoidbrachy Pinacoid 2 010 Prism 4 110 Macro Dome 4 101 Brachy Dome 4 011 Pyramid 8 111
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Common minerals : Zircon, Cassiterite, Rutile are the common minerals Classes of the system Unit forms of Normal class : Form No. of faces Miller Indices Basal Pinacoid 2 001 Tetragonal prism of 2nd order 4 100 Tetragonal prism of 1st order 4 110 Ditetragonal prism 8 hko Tetragonal pyramid of 2nd order 8 101
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Common minerals : Galena, Garnet, Fluorite, Magnetite Classes of the system Unit forms of Normal class : Form No. of faces Miller Indices Cube 6 100 Rhombdodecahedron 12 110 Dodecahedron 8 111 Tetrahexahedron 24 hko (210) Trisoctahedron 24 hhl (221) Trapezohedron 24 hll (211) Hexoctahedron 48 hkl (123)
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We describe the optical properties of the biaxial minerals in terms of three mutually perpendicular directions : X, Y and Z Therefore we can say that “α” has the lowest RI, “β” has the intermediate RI and “γ” has the highest RI, “γ” being highest must be vibrating perpendicular to the optic axis. Optic Plane
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Pseudomorphism is the existence of a mineral that has the appearance of another mineral. Pseudomorph means false form. Pseudomorphism occurs when a mineral alters in such a way that its internal structure and chemical composition changed but its external form is preserved. These mechanism of pseudomorphisms can be explained as follows :-
