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
Volcanic Rock (album) Volcanic Rock (album) Volcanic Rock is the second studio album by Australian proto-heavy metal band Buffalo, recorded and originally released in 1973 on the Vertigo label. The album was stylistically a much harder, heavier and rawer release than its predecessor ("Dead Forever...") – marking a move away from the band's previous progressive rock influences, although retaining a psychedelic element to their sound. "Volcanic Rock" had been recorded effectively as a live-in-the-studio effort, with only vocal and additional guitar overdubs added later during the recording sessions. The album courted controversy with its cover artwork upon its release. Illustrated by J. Phillip