By: magic-gigapans
Image: Paul Karabinos ⧉
License: Copyright, All Rights Reserved

Uploaded: 14 Oct 2020
Last Updated: 14 Oct 2020

886 megapixels
43,308 x 20,456 pixels
144.4 in X 68.2 in at 300dpi
69,244 pixels per inch

Image is 7.5 by 15.7 mm. Plane polarized light. Taken with the automated imaging system at Williams College. Crossed polars: https://viewer.gigamacro.com/view/FBdDNaAFzAyumyMP Rock 12005 is a medium-grained, olivine basalt possessing exceptionally high Mg content. Large pyroxene oikocrysts enclose an early crystallizing assemblage of rounded and embayed olivine. Patches of glomerophyric olivine are present in some areas. Olivine - In this rock, a duality of olivine textures may be noted. Large olivine grains (up to 5 mm) are rounded and embayed and contain relict inclusions; they also have relict skeletal shapes. Smaller, euhedral olivines are poikilitically enclosed within plagioclase or pyroxene oikocrysts. The larger olivines are more magnesian than are the euhedral grains in the plagioclase. Pyroxene - The majority of large pyroxene grains in sample 12005 are composed of augite cores rimmed with low-Ca pyroxene. However, several of the largest include augite plus low-Ca pyroxene grains intergrowths in their cores. Additionally, some partially resorbed olivine grains are partly mantled by low-Ca pyroxene. The relatively complete separation of augite and low-Ca pyroxene on the pyroxene quadrilateral was not observed in other lunar basalts. Plagioclase - Large oikocrysts of plagioclase enclose equant olivine grains. Plagioclase grains are intergrown with pyroxene oikocrysts at their margins. Plagioclase is unzoned An93-86 except where it is alkali-rich at the very edge adjacent to rare segregations of K-feldspar and phosphate. Opaques - Euhedral chromite-ulvöspinel grains and associated metallic Fe occur as inclusions in the olivine. Individual chromites are not zoned to ulvospinel but range in composition throughout the relative crystallization sequence. Intergranular ilmenites poikilitically enclose olivine and pyroxene. Subsolidus exsolution in ilmenite and ulvöspinel are widespread in sample 12005. https://curator.jsc.nasa.gov/education/lpetss/12005.cfm