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Malachite is a copper carbonate hydroxide mineral, with the formula Cu 2 CO 3 (OH) 2.This opaque, green-banded mineral crystallizes in the monoclinic crystal system, and most often forms botryoidal, fibrous, or stalagmitic masses, in fractures and deep, underground spaces, where the water table and hydrothermal fluids provide the means for chemical precipitation.
The soft stone is easily carved and is not degraded by heating. The slick surface of soapstone allows the finished object to be easily removed. Welders and fabricators use soapstone as a marker due to its resistance to heat; it remains visible when heat is applied. It has also been used for many years by seamstresses, carpenters, and other ...
A bell, bell stone or pan was a loose, roughly bell-shaped stone in the mine roof, liable to fall without warning: the cause of many coalmine fatalities. Bells were usually found in shale, but rarely in sandstone. Bevin Boys. Bevin Boys were men conscripted to work in the collieries during World War II in a scheme introduced by Ernest Bevin. [4 ...
The L9 bar mine is a large rectangular British anti-tank landmine.The bar mine's principal advantage is its long length, and therefore its trigger length. A typical anti-tank landmine is circular, and a vehicle's wheels or tracks, which make up only a small proportion of its total width, must actually press on the mine to activate it.
An uncut, rough yellow sapphire found at the Spokane Sapphire Mine near Helena, Montana. Sapphire is one of the two gem-varieties of corundum, the other being ruby (defined as corundum in a shade of red). Although blue is the best-known sapphire color, it occurs in other colors, including gray and black, and also can be colorless.
Corundum is a crystalline form of aluminium oxide (Al 2 O 3) typically containing traces of iron, titanium, vanadium, and chromium. [3] [4] It is a rock-forming mineral.It is a naturally transparent material, but can have different colors depending on the presence of transition metal impurities in its crystalline structure. [7]
Asterism on the surface of a blue star sapphire. A purple-pink star sapphire displaying asterism in a platinum ring.. An asterism (from Ancient Greek ἀστήρ (astḗr) 'star' and -ism) is a star-shaped concentration of light reflected or refracted from a gemstone.
Cordierite or iolite is a magnesium iron aluminium cyclosilicate. Iron is almost always present, and a solid solution exists between Mg-rich cordierite and Fe-rich sekaninaite with a series formula: (Mg,Fe) 2 Al 3 (Si 5 AlO 18) to (Fe,Mg) 2 Al 3 (Si 5 AlO 18). [3]