Yttrium aluminium garnet (Ce:YAG) is used as a phosphor in cathode ray tubes and white light-emitting diodes, and as a scintillator. YAG for a period was used in jewelry as a diamond and other gemstone simulant. Colored variants and their doping elements include: green (chromium), blue (cobalt), red (manganese), yellow (titanium), purple (neodymium), pink, and orange. As faceted gems they are valued (as synthetics) for their clarity, durability, high refractive index and dispersion. The critical angle of YAG is 33 degrees. YAG cuts like natural garnet, with polishing being performed with alumina or diamond (50,000 or 100,000 grit) on common polishing laps. YAG
GemStone IV 2015. "GemStone IV" is a text-based game built on Simutronics' proprietary engine, the IFE (Interactive Fiction Engine). This engine is capable of changing nearly any aspect of the game on the fly which allows updates without the necessity for downtime. Due to the use of the IFE, "GemStone" is rarely taken offline, giving a 24-hour uptime cycle aside from the occasional game crash. The "GemStone" interface is simply a text stream, and the game can be played with a Telnet interface after authentication. There are several official interfaces to the game, as well as several unofficial ones. The oldest interface