I found this rock near my home in the high desert of south central Utah (near Capitol Reef National Park). The sides are symmetrical and smooth -- shaped somewhat like a canoe. It is 6 1/2" long; 1 1/2" at widest point. The top is sheared off and sparkles in the light. It is embedded with flakes of a shiny, black glasslike material, possibly obsidian. The Fremont culture occupied the area and left an abundance of tools, points, and chip rock, many of which were sourced from elsewhere; most likely the result of trading. A neighbor and I came up with an uninformed theory. Would appreciate any informed observations.
Black elongated crystals are mostly hornblendes. The rock itself is (probably) horblende andersite or hornblende dacite. Both are intermediate volcanic rocks.