Gem potential and mineralogical features of apatite from Hormuz Island, southern Iran

Hormuz salt dome (Hormuz Island) is one of the right places for the crystallization of gem minerals, where idiomorphic apatite crystals have been formed under a hydrothermal condition. This island is located in the northern area of the Persian Gulf, south of Iran. The Hormuz Island is composed of salt, anhydrite, sandstone-siltstone, dolomite, limestone, and volcanic horizons. In this research, the Hormuz apatite is assessed in terms of gem potential and mineralogical characteristics. The apatite crystals are formed 2-3 cm in size, mostly transparent and yellow to green, which indicate their gem quality. Considering thermal sensitivity and the moderate hardness of this mineral, the best methods and tools for cutting were selected through multiple testing methods. According to our research, the best approach to a fantasy or cabochon cut is the use of a 0.3 mm thin edge, 220 or 240 grit sanding discs, a 400 grit abrasive for scratch removing and 800, 1200 and 2500 grit abrasives for polishing. Respectively, use of water in all stages of sawing, cutting and polishing is necessary.