Mineral name:  Celestite on limestone Chemical formula:  SrSO4 Location:  Travis County, Texas  Crystal system and class:  Orthorhombic  2/m2/m2/m Genesis: These well-formed celestite crystals were precipitated from aqueous solutions on the walls of solution cavities in limestone. Width and length of specimen in field of view in cm:  3 x 6 Specimen number:  E