Garnet not like sapphire blue in subdued daylight but more reminiscent of the grayish blues and greenish blues sometimes seen in spinel. However, in white LED light, the color is equal to the best cornflower blue sapphire, or D block tanzanite; this is due to the blue garnet's ability to absorb the yellow component of the emitted light. Pyrope is an indicator mineral for high-pressure rocks. The garnets from mantle-derived rocks, peridotites, and eclogites commonly contain a pyrope variety. Spessartine or spessartite is manganese aluminium garnet, MnAl(SiO). Its name is derived from Spessart in Bavaria. It occurs most often in granite
Gemstone irradiation the country. All neutron- or electron beam-irradiated gemstones must be tested by an NRC-licensee prior to release for sales. In India, the Bhabha Atomic Research Centre started irradiating gemstones in the early 1970s. In Thailand, the Office of Atoms for Peace (OAP) conducts the process for private sectors, irradiating of gemstones from 1993 to 2003. The most commonly irradiated gemstone is topaz, which becomes blue after the process. Blue topaz is very rare in nature and almost always the result of artificial irradiation. According to the American Gem Trade Association, approximately 30 million carats () of topaz are irradiated every