Crystalline order found in the strangest of places

If you look carefully at the “blobs” in this exhibit, you will see hexagonal shapes. These are crystals of calcite, but unusual in that they are filled with fine sand. Sand crystals like these grow within permeable sediments by precipitating around a nucleus. Because the sand is so porous, the crystal lattice is not affected by the sand grains and builds near-perfect crystals. Sand crystals are rare, but found in abundance in some localities in Dawes and Sioux counties.

The specimen in this exhibit is from the collection of the late Dr. Kenneth Ohme of Mitchell, Nebraska.