Quoting from the Trimingham collection card (which accompanies the specimen): "An attractive cluster of divergent blades translucent gray-brown [crystals with] white rims. No matrix. Displays well." The white rims are very likely due to heating with a torch (a common practice with Mexican gypsum of low quality). Superb white fluorescence with both longwave UV (blacklight) as well as shortwave UV. In addition, the specimen continues to glow (phosphorescence) green for several seconds after the longwave UV is extinguished. The specimen is in excellent condition.