A can be magnesium, iron, manganese or calcium, B is iron or aluminium (occasionally chromium). Commonly found in metamorphic and occasionally igneous rocks.
An isotropic mineral appears opaque in thin section in polarised light.
Other meanings:
Materials: In the study of mechanical properties of materials, "isotropic" means having identical values of a property in all crystallographic directions.
Optics: Optical isotropy means having the same optical properties in all directions.
The way in which a mineral shines in light and described using terms such as vitreous, adamantine, etc. However, there are no rigid boundaries between the different terms.
A mineral with the outward form/shape of another species of mineral that it has replaced. There are three types of replacement: infiltration pseudomorph, paramorph, and encrustation pseudomorph.
Silicatemineral composed of chains of silica tetrahedra. Cations occupy the sites between oxygen atoms. The general formula is: A1-x(B,C)1-xT2O6. A is commonly sodium or calcium, B is magnesium or iron (2+), C is aluminium or iron (3+) and T is silicon or aluminium. It is common in igneous and metamorphic rocks.
A mineral which has subsequently formed in-situ due to secondary processes, such as oxidation or weathering. A good example is the alteration of olivine to secondary chlorite and serpentine.
GeologyRocks