The name spinel may come from the Latin spinal or “thorn,” referring to the triangular shape of the crystal faces, from the Greek root spinter, meaning spark, presumably referring just to the red variety. Like ruby and garnet, it has also been called carbuncle, from the Latin carbuncles, or small coal. However, recognition that the various types of carbuncle, differed in hardness, led to their being value accordingly. Undesirable confusion has been created by the alternative name of ruby spinal. And infact, some of the largest and the most famous rubies in the world, such as the black princess ruby in the English crown jewels, are rarely spinals, not corundum’s.



Appearance:
Spinel may be an intense, bright red like ruby, but more often tends to be brick red, almost orange. It can have violet tinge, and such stones were formally refer to as Balas ruby, after the Badakshan (Balascia) reason of Afghanistan where they were found. The color is often soft: pink rather than red. Spinel has good luster and transparency. It is generally given a mixed, oval or round cut, alternatively, a square or rectangular, step or trap cut.



Distinctive features:
Red spinel is fairly similar to ruby; the red color fluoresces slightly in bright light, but much less than ruby. Being singly refractive, it is not pleochroic. This feature is in contrast to ruby but in common with garnet, although the latter is nearly always a rather dull color, which is not heightened even by strong light. It can be hard to distinguish spinal from either of these gemstones, in which case the physical properties will need to be measure. However, spinel may contain several parallel rows of minute octahedral crystals of hessonite (iron spinel), which are highly distinctive and sometimes recognizable with an ordinary lens. Soft pink varieties can be hard to distinguish from some tourmalines, although the latter display varying degrees of birefringence, and have different physical properties.



Occurrence:
Red and pink spinels come from Mogok region of Burma and Afghanistan. Spinels may also come from Sri Lanka and Thailand, where they are found together with corundum.



Value:
As secondary gems go, brilliant red spinel comparable in color to rubies is quite valuable, though they are only one-tenth or so the price of rubies themselves. Pale pink or violet spinels; accept for particular fine or large specimens are of much lower value.



Simulants and Synthetics:
Synthetic spinels in many colors has been widely produced by the flame fusion method, but owing to difficulties in obtaining the red variety, the only examples found are extremely rare and of small size-are a maximum of 1carat or little more. These are distinguished from the natural variety by the typical internal structures and inclusions produced by the Vernuil method. Recently, synthetic red spinel has also been produced by the more costly flux melt process, but it has not proved economical.