This is honeycomb calcite... It grows in only one place in the world!

High in the Uinta Mountains of northeastern Utah is the only known location in the world to find recently discovered honeycomb calcite.

The honeycomb name comes from the appearance of this calcite -- once the surface is polished. The gold cells and whitish "cell borders" of honeycomb calcite are formed by the growth of long, fibrous tubular cells and crystals of honey color outlined by membranes surrounding each cell. Depending on how the calcite starts to form, it takes on different appearances, from small, tightly bunched cells to wide cell areas.

Honeycomb calcite is often used to provide a dramatic accent to buildings and architectural applications. It is crafted into many jewelry works and ornaments. The honey-colored transglucent appearance of the stone makes it hold and diffuse light, so it is often used as polished jewelry, candle holders, or backlit walls, baths, bowls or countertops.

Image from honeycombcalcite.com