Spinel

SpinelSpinel is not a well-known stone, but this mineral is most often mentioned in the context of external similarity with rubies. Spinel is a very hard stone and has a number of distinctive features, which should be noted.
The name of this mineral has no unambiguous interpretation. It has been suggested that the word “spinel” is derived from “spinella”, or from diminutive form of the Latin word “spina”, meaning “thorn.” The second assumption is related to its derivation from the Greek word for “spark”. It is known that red spinel is called “balas ruby”: from the Latin “balascus”, which comes from the Arabic “Badakshan” – the name of the area, where the most beautiful stones of spinel were mined in the Middle Ages. Another common name is “rubicelle” derived from the French “rubis” meaning “ruby”.

Formation of spinel

Formation of spinelIn nature spinel often occurs as overgrown crystals in the form of octahedrons, and in placer deposits rounded crystals can be found. The mineral is formed in metamorphic rocks, which result from changes of temperature or pressure – for example, in the marbles, calc-silicate rocks and placer deposits. Noble spinel in the form of transparent crystals of different colors occurs in crystalline limestones and crystalline schists, as well as in alluvial deposits, which appear as a result of their ablation. Unlike sapphire and ruby, spinel is a little softer.

Spinel coloring

Spinel is characterized by a multitude of colors. For example, noble spinel can be represented by red, brown, blue, black or colorless transparent crystals. Ruby spinel is characterized by intense red color and “rubicelle” by orange-red. “Balas ruby” has a pinkish tinge. Stones with purple coloring are called oriental amethyst. Blue spinel (or sapphire spinel) is very rare. It is also characterized by a bit steel shade. Common spinel is also called pleonaste (from the Greek “abundant” probably due to many facets of stone). Spinel coloringThis type is typically of dark brown, dark green, or even a black color. Common spinel occurs more often than other varieties, and mostly in the form of large crystals. Chrome spinel is called picotite. It has a dark, almost black color. The spinel type with so-called alexandrite effect is very curious: in daylight the stone will be blue and under the light bulb the purple-violet hue will appear. Stones of beautiful blue color, sometimes with a subtle purple tint, are called gahnospinel. Violet-red samples are known as almandine spinel, but also “almandish” with purplish-red color is attributed to garnets.

The use of spinel

The stones with intense red color are the most valuable for jewelers. Spinel has vitreous luster. For the manufacture of various products the stone is given diamond, trap or combined cut, as well as cabochon shape. This stone is used to create jewelry, souvenirs, but mostly in the form of inserts and inlays – for example, in mosaics and panel pictures. And the stones, which are not suitable for jewelry, are used to create clockworks and abrasive materials.

Deposits of spinel

Deposits of spinelNoble spinel is mined in Ceylon, the island of Borneo, as well as in India, Brazil and Afghanistan. Spinel samples are found in alluvial deposits of Chantabun (Thailand) – together with sapphires and rubies. In addition to the red rocks, in Ceylon also occur beautiful purple and blue minerals, and the variety of black color is also called ceylonite. One of the oldest deposits of spinel is Badakhshan mines (Pamir).