Spinel occurs in irregular grains that appear to fit in among the olivines. It has high relief and is deep olive brown in plane light. It is isotropic under crossed polars. These aggregates are interpreted as crystallized partial melt, approximating alkali basalt in composition, that formed in the mantle, possibly prior to inclusion in the basalt magma. Most of what you see is isotropic glass formed by quenching melt, and holes or vesicles .
Plagioclase occurs as tiny, needle-like microlites .
Mantle xenocrysts include angular fragments of olivine, orthopyroxene grains with lobate dissolved borders, spinel rimmed by crystallized melt, and a lherzolite xenolith. Xenocrystic plagioclase may be a fragment of crustal rock. Matrix is serpentine, but cannot be identified at this scale. Olivine in the peridotite may be recognized by its glassy olive green appearance and lack of cleavage. Kimberlite is an igneous rock made up of angular clasts of olivine in matrix of broken olivine, phlogopite, carbonate and serpentine.