A small piece of Earth's upper mantle from ~75 km-depth
peridotite from the subcontinental lithosphere below southernmost Patagonia,
Demouchy, S., S.D. Jacobsen, F. Gaillard, and C.R. Stern (2006) Rapid magma ascent recorded by water diffusion profiles in mantle olivine. Geology 34, 429-432. PDF
This rock represents "fertile" upper mantle with olivine (light-green) orthopyroxene (dark-green or brown) clinopyroxene (Cr-diopside, emerald-green) and garnet (red). The bulk composition is close to Ringwood's "pyrolite". A partial melt of this material would produce basalt.
I made this image (left) on a flatbed scanner.
Photo edge is about 5 cm
Below: Series of polarized (E//a) infrared spectra measured across an olivine grain from Pali-Aike (PA-7). Rims depleted of hydrogen are interpreted to be evidence for dehydration during ascent. Does the mantle contain more water than we thought? This is Figure 3 of Demouchy et al. (2006).