This is an unusually large plate of rare Calaverite (gold telluride) crystals from the classic Cripple Creek district, which hit its heyday over 100 years ago. Interestingly, you can see bands of silver ore running htrough the matrix, too! This is an extremely rich plate of large size and with MANY eye-visible crystals (to 3-4mm) and veins shooting through. The crystals are, many of them, freestanding in a protected seam along the face (a good indication that this is not sylvanite, which tends to be both more reticulated in habit and more embedded in matrix). It came to me from a museum deaccession.