I found this in a stream in Medicine Bow-Routt National Forest, Wyoming. One side (2/3 length) has a pointy pyramid with four faces; other side (1/3 length) has four faces but with with an edge instead of a point. Color ranges from dark chocolate brown to black with a lacquer-like finish. It interacts very weakly with a rare earth magnet.
closed as off-topic by trond hansen, JulPal, Peter Jansson, Semidiurnal Simon, Gimelist Jan 25 at 23:44
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Your specimen might be a monazite crystal. The color, weakly magnetic and general crystal form would match monazite. The crystal system for monazite is monoclinic which offers a possible explanation for the specimen's asymmetric appearance.
There are plenty of granitic rock in the Medicine Bow-Routt National Forest area