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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.
It is typically blue, but natural "fancy" sapphires also occur in yellow, purple, orange, and green colors; "parti sapphires" show two or more colors. The only color corundum stone that the term sapphire is not used for is red, which is called a ruby. [1] Pink colored corundum may be either classified as ruby or sapphire depending on locale.
A star sapphire is a type of sapphire that exhibits a star-like phenomenon known as asterism; red stones are known as "star rubies". Star sapphires contain intersecting needle-like inclusions following the underlying crystal structure that causes the appearance of a six-rayed "star"-shaped pattern when viewed with a single overhead light source.
Sapphirine is a rare mineral, a silicate of magnesium and aluminium, with the chemical formula (Mg,Al) 8 (Al,Si) 6 O 20 (with iron as a major impurity). Named for its sapphire-like colour, sapphirine is primarily of interest to researchers and collectors: well-formed crystals are treasured and occasionally cut into gemstones.
The five cardinal gems. Clockwise from top: sapphire, ruby, emerald, amethyst, diamond. Cardinal gems are gemstones which have traditionally been considered precious above all others. The classification of the cardinal gems dates back to antiquity, and was largely determined by ceremonial or religious use as well as rarity. [1]
Book of Exodus 28:16–20 cites following decorative stones (list of precious stones in the Bible): (the "breastplate" or "rational" of the Jewish High Priest) It shall be foursquare and doubled: it shall be the measure of a span both in length and in breadth. And thou shalt set in it four rows of stones: in the first row shall be a sardius ...
The term three phase relates to the three phases of matter, solid, liquid, and gas. This is a three phase inclusion in rock crystal quartz. The solid is a black material that is of bituminous origin. The liquid encased is petroleum, and the gas bubble is methane. Inclusions are one of the most important factors when it comes to gem valuation.
A telltale characteristic is the Verneuil crystal is curved growth lines (curved striae) form, as the cylindrical boule grows upwards in an environment with a high thermal gradient, while the equivalent lines in natural crystals are straight. Another distinguishing feature is the common presence of microscopic gas bubbles formed due to an ...