This is a Calcite specimen from the famous Elmwood Mine in Carthage, Tennessee. This mine is closed, so pieces are becoming harder to find on the open market. This particular piece is a double terminated dogtooth style crystal with exceptional clarity near the tip. The color is more concentrated along the outermost layers of growth, which you can see from the side view of the crystal.
This piece measures approximately 5.9 x 3.9 x 3.7 cm and comes with a display card listing the mineral name and locale.