Watson 013        30°34’30.0"S, 131°30’5.9"E

South Australia, Australia

Found: 14 Apr 2010

Classification: Ordinary chondrite (H3)

History: Single piece found by A. Tomkins on the Nullarbor Plain.

Petrography: (A. Tomkins, Monash) Well-defined chondrules (most <1 mm, some to 2 mm) in a highly porous light-colored transparent matrix; there is no matrix glass. Plagioclase to 20 μm. Chondrule types include RP, POP, PP, BO and PO; there are rare very finely recrystallized glassy chondrules. Chondrule mesostases finely recrystallized (<1 μm). The porosity is variable, being more porous in zones where <5% of metal is rusted, less porous in domains where metal is >20% rusted. Fe-Ni metal grains (10-15%) are variably irregular and approximately twice as abundant as troilite, with which they are occasionally conjoined. Most conjoined metal-troilite grains have sharp contacts, and there are rare domains of troilite in metal with adjacent Cu metal. Olivine grains show sharp extinction.

Geochemistry: (A. Tomkins, Monash) Microprobe analyses show that olivine and pyroxene compositions are highly heteorgeneous: olivine Fa_18.6-28.1, mean=20.7 mol%, std=4.1, n=5; Low-Ca pyroxene Fs_9.3-17.9, mean=15.7 mol%, std=3.2, n=5; Wo_0.6-4.0. Average compositions are most consistent with a H chondrite designation.

Classification: Ordinary chondrite (H3, S2, W1). The type 3 classification is based on the heterogeneity of olivine and pyroxene compositions; the glass recrystallization implies upper type 3.