CA66AI4: Group of crystals, one of them clearly dominant and all them (except one) doubly terminated. They show a prism with curved edges and a poorly defined terminal rhombohedron. The crystals are completely filled by sand inclusions. An American classic that is currently difficult to obtain in good samples because the area where they are found has been declared a National Park.
Rattlesnake Butte, Jackson County, South Dakota  USA (±1990)

Specimen size: 7.7 × 5 × 3.9 cm = 3.03” × 1.97” × 1.54”

Main crystal size: 7.2 × 3.2 cm = 2.83” × 1.26”