Grossular from Sierra de las Cruces, Mexico – Yellowish-Gray Crystal

This Grossular from Sierra de las Cruces near Sierra Mojada in Coahuila, Mexico shows a compact yellowish-green crystal with clearly recognizable dodecahedral faces. The crystal form is not completely regular, but is structured by intergrowths and a pronounced re-entrant angle.

With dimensions of 3.1 × 2.7 × 2.5 cm and a weight of 40.3 g, this is a Miniature specimen. The subdued yellowish-green coloration and the more complex crystal morphology distinguish the specimen clearly from more uniformly developed Grossular single crystals from the same locality.

Dodecahedral Grossular with complex intergrowth

Several larger crystal faces clearly show the typical dodecahedral development of Grossular. At the same time, the surface is structured by offset crystal sectors and stepped transitions.

A particularly striking feature is a distinct re-entrant angle between two crystal areas. This gives the specimen an unusual morphology. Twinning cannot be confirmed solely from the external crystal form, which is why the specimen is deliberately described here as showing a complex crystal intergrowth.

The crystal faces show a weak to moderate luster. In color, the Grossular ranges from pale yellowish green to grayish green, with some areas appearing slightly lighter.

Grossular from Sierra de las Cruces in Coahuila

Sierra de las Cruces near Sierra Mojada in Coahuila is one of the classic Mexican localities for Grossular. Both individual dodecahedral crystals and more strongly intergrown crystal aggregates are known from this locality.

This specimen is especially interesting because of the combination of yellowish-gray coloration, dodecahedral faces, and complex intergrowth. The pronounced re-entrant angle makes the crystal morphology easy to follow from several viewing directions.