Rocks or minerals lacking crystal structure or form
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Tag: <span>A</span>
A variety of translucent to transparent purple to grey coloured quartz common as a semiprecious gemstone. The color results from with ferric iron substitution for silicon
The surrounding or encompassing and current state of an area
The formation of usually fossilized amorphous hydrocarbons from ancient tree resins, having highly variable C:H:O ratios
A bright green or blue green variety of microcline sometimes cut as semi precious stones and for ornamental use
Alloys of mercury with one or more metal
A light, silvery-white, ductile metal with high electrical conductivity and high resistance to oxidation. Symbol, Al
Physical and chemical changes in a rocks or mineral subsequent to initial formation, and to a lesser degree than metamorphosis
Positively charged particles emitted from radioactive material
An orthorhombic mineral, Al2SiO5; its transparent green variety is used as a gem