Classic light blue angelite, presented as a "window"  -  a top-polished piece that lets the beauty of the angelite shine through. Angelite is a trade name for a semi-transparent light blue-grey fine-grained anhydrite marketed as a gem material from Peru.

Miniature specimen: about 2.0" x 1.8" x 0.8" (50mm x 45mm x 20mm).