Corundum
Some varieties of corundum are natural gemstones. The ruby
and sapphire are the varieties most commonly used in jewelry. Emery variety of
this stone is a ceramic widely used, mainly as an abrasive because of its
hardness, and as refractory. Corundum is the second hardest natural mineral
after diamond. Corundum is used in some sharpening stones, but also in all
kinds of wheels.
Cornelian
The Carnelian is a variety of quartz red to red-brown in the
group of red chalcedony. It is mainly used for jewelry. When buying carnelian,
we must be vigilant because most stones are actually proposed tinted agates.
The Carnelian is a stone of solid color, while the colored agates presented
often have multi-colored lines.
Diamond
Diamond is a mineral composed of carbon. This is the hardest
of all natural materials. They form when it is under conditions of temperature
and pressure very high, corresponding to depths of about 180 km in the mantle.
Ten tons of ore can be extracted only one carat diamond. In general, square
kilometers of land is excavated for a size able rock, hence the cost of
diamonds. The beauty of his brilliant is because it has a high refractive index
of light and a large dispersive power. But all diamonds are not used in
jewelry. Any failure can deprive them of the value and they are then used to
craft applications. Because of its extreme hardness, diamonds can be machined
only by another diamond, so the sculpture and the polish of the stone are the
most important elements. There are many ways to cut the diamond, but one that
is best in the beauty of the diamond is certainly the size "brilliant"
that turns rough stones into gems of light, showing 58 facets.
Use: invulnerability to undead.
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