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Smithsonian National Museum of Natural History

Sinuous Gypsum

Photograph of a sinuous gypsum (NMNH R13219) from the National Mineral Collection
Photo by Chip Clark. Click to zoom.
Catalog Number NMNH R13219-00
Locality Chihuahua, Mexico

Gypsum is a relatively common mineral. It is used in construction as drywall and an ingredient in plaster and fertilizer. The name is derived from the Greek gypsos, meaning “chalk or plaster.” Gypsum is typically colorless to white, but due to impurities it can occur in shades of yellow, blue, pink, brown or gray.  It commonly forms as flat, elongated prismatic crystals that are mostly transparent. Fed by a mineral rich solution that seeped through the rock, this sinuous specimen of gypsum grew from the wall of a cave. The “ramshorns” occurred as some crystal strands grew faster than others.



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