This is the polished on the one side greenish-gray tinguaite specimen. Dimensions: 2.6 x 2.0 x 1.6″ (6.6 x 5.2 x 4cm). Weight — 7.5oz (214 grams). Origin: Russia, Kola Peninsula.
Some information about tinguaite:
Tinguaite is an undersaturated, medium-to coarse-grained, igneous rock consisting of essential alkali feldspar, nepheline, and aegirine (with or without sodic amphibole or biotite). Tinguaite is the hypabyssal equivalent of phonolite.