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
Grammy Award for Best Rock Performance Grammy Award for Best Rock Performance The Grammy Award for Best Rock Performance is an award presented at the Grammy Awards, a ceremony that was established in 1958 and originally called the Gramophone Awards. According to the 54th Grammy Awards description guide it is designed for solo, duo/groups or collaborative (vocal or instrumental) rock recordings and is limited to singles or tracks only. This award combines the previous categories for Best Solo Rock Vocal Performance, Best Rock Performance by a Duo or Group with Vocal and Best Rock Instrumental Performance. The restructuring of these categories was a result of the