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 Female Rock Vocal Performance Originally called the Grammy Award for Best Rock Vocal Performance, Female, the award was first presented to Donna Summer in 1980. Beginning with the 1995 ceremony, the name of the award was changed to Best Female Rock Vocal Performance. However, in 1988, 1992, 1994, and since 2005, this category was combined with the Grammy Award for Best Male Rock Vocal Performance and presented in a genderless category known as Best Rock Vocal Performance, Solo. The solo category was later renamed to Best Solo Rock Vocal Performance beginning in 2005. This fusion has been criticized, especially when female performers are not