Taaffeite has properties that are very similar to spinel such as hardness, density and index of refraction and is therefore difficult to distinguish from the much more common gemstone spinel. Its the double refraction that is the key and the only way that most of the gem quality taaffeite has been found among the other gemmy grains found in alluvial deposits in Sri Lanka. Some lower grade taaffeite has been found in China associated with fluorite. Luster is vitreous to adamantine. Crystals are transparent to translucent.
Crystals are limited to alluvial grains.
Cleavage is absent. Streak is white. Associated Minerals include other alluvial gemstones such as spinel and also with fluorite. Notable Occurrences include the alluvial deposits in Sri Lanka and sediments in China Best Field Indicators include double refraction, hardness, locality and color.