BH250-8
Title
Subject
Description
Minor Mineral: clinopyroxene altering to chlorite, sanidine, titanite, sericite, calcite, apatite
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BH250-8 is a strikingly beautiful tuff with rich mineralogical features. It contains basaltic hornblende—some crystals showing zoning—as well as both orthopyroxene (OPX) and clinopyroxene (CPX), with some CPX grains displaying anomalous interference colors. Scattered quartz grains are also present. Plagioclase feldspars exhibit alteration to sericite, while portions of the pyroxene have altered to chlorite. Accessory minerals include sphene (titanite) and exceptionally large, well-formed apatite grains—some cut parallel and others perpendicular to the c-axis, clearly revealing basal cleavage. Secondary calcite occurs along veins and voids, and the groundmass contains devitrified and recrystallized volcanic glass. This is a particularly beautiful and mineralogically diverse sample.
There are several apatite crystals cut parallel to the C-axis that can be used to determine, length fast, length slow optical property as seeing in the video.