 | HYPERTHSTINE | Hardness | -5-6 | | Color | -Dark Grey to Black | | Origin | - | | Transparency | -Opaque | | |
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| These minerals, belonging to the pyroxene group, are employed in jewelry when, on account of a fibrous structure or a regular arrangement of inclusions, they exhibit a chatoyant effect. They do not afford transparent stones, but are cut en cabochon to make cat's-eyes and give other schillerizing effects.
The light which plays over it is copper-red in color, and very brilliant in a good stone. The cause of the chatoyancy is supposed to be countless crystals of the oxide of titanium, known as brookite, which are arranged in regular order in the stone. The stone must be cut with reference to the direction of these in order to give the chatoyant effect.
The hypersthene used for this purpose comes almost exclusively from the Island of Paul on the coast of Labrador. Here it occurs together with labradorite as shore pebbles, and it may also be quarried from neighboring cliffs. For cutting, a sound piece without flaws must be used, and it is often necessary to break a number of fragments before a suitable one can be found. Yet the supply of material is so abundant and the demand comparatively so limited that the stones do not command a high price.
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