Found 2003, October
Carbonaceous chondrite (Bencubbin-like meteorite) (CBb)
One stone, weighing 16 kg, was found by a tractor driver in a field
during harvest carrying in the Ishimbai region of Bashkortostan, close
to the Isheyevo village. A small piece of the meteorite was issued to
the Vernadsky Institute by Kazakov D.A., and Polozkov A.G, September
2004. Mineralogy and classification (Ivanova M.A. Vernad., Ulianov A.A.
MSUM). Fusion crust is well developed, dark brown. The meteorite
consists of FeNi metal grains, C, POP, rare BO chondrules (0.02-1 mm in
size), chondrule fragments, CAIs, and matrix lumps. FeNi metal comprises
from 50 to 70 vol%, and contains 4.2-8.4 wt% Ni, 0.2-0.5 wt% Co, and
0.03-0.6 wt% Cr; Co/Ni ratio is approximately solar. C chondrules donít
contain any FeNi metal grains, they are Mg-rich, and consist of
pyroxene-rich cryptocrystalline material. Olivine, Fa2.5, rare FeO-rich
olivines, Fa10-38 ; pyroxene, Fs2.1Wo1.7 , FeO-rich pyroxene,
Fs8-12Wo0.8-1.8; troilite is Cr-rich, 2.5 wt% Cr. INAA data for a 20 mg
chip: 2.74 wt.% Ni; 717 ppm Co; 2608 ppm Cr, 8.2 ppm Sc, and 1.59 ppm
Ir. Petrological type 3; shock stage, S1; weathering grade, W1.
Specimens: a type specimen, 24.3 g, and two sections, Vernadsky; main mass
with anonymous finder.
Isheyevo is unique in that it is almost all metal in
the matrix, and still has large chondrules and chondrule fragments.