Quartz-pyrite pseudomorph found at Lassen Volcanic's Sulphur Works

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Quartz-pyrite pseudomorph found at Sulphur Works

Quartz-pyrite pseudomorph found at Sulphur Works, Loomis Museum, Lassen Volcanic National Park
Quartz-pyrite pseudomorph found at Sulphur Works
and now at display in the Loomis Museum

The shown pseudomorph specimen is displayed at the Loomis Museum with the following description:

This pseudomorph is a quirky combination of milky-colored quartz and dull-gray pyrite. It was found at the Sulphur Works and has the look of unshorn wool.

The geothermal Sulphur Works area is located in Lassen Volcanic National Park, about one mile north of its southwest entrance and a few miles southwest of Bumpass Hell.

Quartz is an important rock-forming mineral that appears in different crystalline forms as well as colored varieties (for example, see The Quartz Page)—and in combination with other minerals. In a pseudomorph (literally meaning “false form”) a mineral replaces the structure and composition of another mineral with its own, but preserves the outward shape of the original mineral. The usual mineralogical terminology for a pseudomorph is “replacer after original.” Such a designation syntax, unfortunately, is not used in the description of the specimen above. Quirky!