Birch Mountains kimberlite field shales interbedded with kimberlite at some of the diatremes are consistent with a Late Cretaceous age (Late Albian to Maastrichtian). The volcanic rocks of the BM field consist primarily of crater-facies pyroclastic kimberlite and resedimented kimberlite. They include massive layers, as well as bedded and graded layers of coarse lapilli alternating with layers of finer tuff. Lapilli and olivine phenocrysts are set in a grey-green matrix of serpentine, carbonate minerals (calcite, dolomite and magnesite) and clay minerals. Phlogopite, oxide minerals (ilmenite, perovskite and spinel), apatite and pyrite are also present. Diamonds and microdiamonds have been recovered from samples taken from
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