BH250-231a
Title
Subject
Description
Major Minerals: diopside, olivine, plagioclase
Minor Minerals: titanaugite, oxides
Optics: Euhedral olivine, pyroxenes, and plagioclase feldspars are present. Many of the olivine and pyroxene grains are cut perpendicular to their optical axes and display beautiful interference figures. Some olivines exhibit undulose extinction, indicating deformation in the molten magma. Well-developed Carlsbad twinning is observed in olivine, pyroxenes, and plagioclase.
Texture: Porphyritic with phenocrysts in a fine-grained groundmass; agglomerated crystal clusters and vesicular features are present. In hand sample, some phenocrysts measure up to 1.5 centimeters in diameter.
Hand Sample: This rock is mapped as an ankaramite, a rare, mafic to ultramafic, dark-colored volcanic rock that is notably rich in large mafic phenocrysts, particularly olivine and clinopyroxene (diopside). It is named after Ankaramy, a locality in Madagascar where it was first described.