Rocks and Microscopy > Chondrite meteorite (NWA 7308) thin section in cross polarised light by Ian Butler

NWA7308 is an LL3 ordinary chondrite from North West Africa, found in 2012. The gigapan comprises 113 images taken on a Nikon D60 using direct eyepiece projection from a Zeiss microscope and luminar objective. The image was put together using PTGUI.

ordinary chondrite: A major class of chondrites, distinguished by sub-solar Mg/Si and refractory/Si ratios, oxygen isotope compositions that plot above the terrestrial fractionation line, and a large volume percentage of chondrules, with only 10-15 vol% fine-grained matrix.

LL group: The low-iron, low metal (LL) chemical group of ordinary chondrites, distinguished by their low siderophile element content, fairly large chondrules (~0.9 mm), and oxygen isotope compositions that are further above the terrestrial fractionation line than those of other ordinary chondrites. .

type 3: Designates chondrites that are characterized by abundant chondrules, low degrees of aqueous alteration, and unequilibrated mineral assemblages. Many of the low-Ca pyroxene grains are monoclinic and exhibit polysynthetic twinning. The type 3 chondrites may be divided into subtypes ranging from 3.00 (least metamorphosed) to 3.9 (nearly metamorphosed to type 4 levels). If primary igneous glass occurs in the chondrules, it belongs to type 3.

(Thanks to the Meteoritical Society for the definitions)