Naica, Mun. de Saucillo, Chihuahua, Mexico

9 x 8.4 x 6.8 cm
3.5 x 3.3 x 2.7 in

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This specimen is a bit of a mystery. Much of the specimen is composed of elongated, twinned Gypsum crystals which have pseudomorphed to Quartz. However, the large, compound central crystal is partially composed of Quartz with Calcite in the center. It appears this is an unusual case where Calcite has replaced Gypsum, which although observed in the laboratory, it is much more common in natural specimens for Gypsum to replace Calcite. If anyone has any ideas as to how this came about, or seen a similar specimen, please let me know.

Condition: Good

Flaws: One edge of the largest crystal is cleaved as well as the edges of some of the smaller crystals. These cleaves are all facing the same direction. With the exception of the largest crystals, these cleaved surfaces are Quartz, indicating the cleaving preceded the replacement with Quartz. On the largest crystal, part of the cleaved surface is Quartz and the rest is honey brown colored Calcite.

This mineral is also found in the following galleries: Minerals From Mexico | Calcite | Quartz | Minerals Priced Between 50 and 99 Dollars