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 Album Grammy Award for Best Rock Album The Grammy Award for Best Rock Album is an award presented at the Grammy Awards, a ceremony that was established in 1958 and originally called the Gramophone Awards, to recording artists for quality albums in the rock music genre. Honors in several categories are presented at the ceremony annually by the National Academy of Recording Arts and Sciences of the United States to "honor artistic achievement, technical proficiency and overall excellence in the recording industry, without regard to album sales or chart position". The award for Best Rock Album was first presented to the