Selenite; Ram's Horn crystals - Chihuahua, Mexico (MS-2631a)
Hand-sized specimen showing multiple classically-curved crystals. Measures about 12cm x 7cm x 6cm. Weighs about 420 gms. The yellow cube in some of the photographs is a typical bullion cube of about one-half inch on a side; included for size reference.
Will fit in a Medium USPS Priority Mail Flat Rate box