This is the polished amphibolite pebble. Dimensions: 3.1 x 1.8 x 0.6″ (8 x 4.5 x 1.4cm). Weight — 4oz (113 grams). Origin: Russia, Siberia.
Some information about amphibolite:
Amphibolite is a metamorphic rock that contains amphibole, especially the species hornblende and actinolite, as well as plagioclase.
Amphibolite is a grouping of rocks composed mainly of amphibole and plagioclase feldspar, with little or no quartz. It is typically dark-colored and dense, with a weakly foliated or schistose (flaky) structure. The small flakes of black and white in the rock often give it a salt-and-pepper appearance.