Ultramafic rock but there are ultrapotassic and highly silica-under-saturated rocks with >18% MgO which can be considered "ultramafic". Ultrapotassic, ultramafic igneous rocks such as lamprophyre, lamproite and kimberlite are known to have reached the surface of the Earth. Although no modern eruptions have been observed, analogues are preserved. Most of these rocks occur as dikes, diatremes, lopoliths or laccoliths, and very rarely, intrusions. Most kimberlite and lamproite occurrences occur as volcanic and subvolcanic diatremes and maars; lavas are virtually unknown. Vents of Proterozoic lamproite (Argyle diamond mine), and Cenozoic lamproite (Gaussberg, Antarctica) are known, as are vents of Devonian lamprophyre (Scotland). Kimberlite
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