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The powdered gem mineral is then melted (or a metallic mixture directly burned in an oxygen flame) the residue of which then drips through a furnace onto a boule. The boule where the corundum or spinel cools down and crystallizes, spins and thus causes the curved striations, which are diagnostic for a lab-created gem: Natural corundum does not ...
A gemstone (also called a fine gem, jewel, precious stone, semiprecious stone, or simply gem) is a piece of mineral crystal which, when cut or polished, is used to ...
An asterism (from Ancient Greek ἀστήρ (astḗr) 'star' and -ism) is a star-shaped concentration of light reflected or refracted from a gemstone. It can appear when a suitable stone is cut en cabochon (i.e. shaped and polished, not faceted). A gemstone that exhibits this effect is called a star stone or asteria.
However, the argument for the Sanskrit origin is strong. The term first appears in Roman references around 250 BC, at a time when the opal was valued above all other gems. The opals were supplied by traders from the Bosporus, who claimed the gems were being supplied from India. Before this, the stone was referred to by a variety of names, but ...
A gem graded none on the enhancement scale may still exhibit visible inclusions. Laboratories apply these criteria differently. Some gemologists consider the mere presence of oil or polymers to constitute enhancement. Others may ignore traces of oil if the presence of the material does not improve the look of the gemstone. [19]
Examples of it have been appreciated for its color and natural beauty since the Neolithic times, [1] and worked as a gemstone since antiquity. [2] Amber is used in jewelry and as a healing agent in folk medicine. There are five classes of amber, defined on the basis of their chemical constituents.
The current definition, sometimes known as the metric carat, was adopted in 1907 at the Fourth General Conference on Weights and Measures, [1] [2] and soon afterwards in many countries around the world. [i] The carat is divisible into 100 points of 2 mg. Other subdivisions, and slightly different mass values, have been used in the past in ...
In South American folklore, the carbuncle is a small elusive animal containing a mirror, shining gemstone or riches like gold. [4] [5] The description of the carbuncle vary, some saying it looks like a firefly in the night, or like having a bivalve-like shell and maize ear shape. [4]