Where is Gypsum found?
CaSO4·2H2O
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Open the appGypsum occurs in specific geological environments. Knowing where to look, and in what kind of rock, is the difference between going home empty-handed and finding a great specimen.
Where to find Gypsum
Naica Mine, Chihuahua, Mexico
Famous for its giant selenite crystals, some of the largest natural crystals ever found, in the 'Cave of Crystals'.
White Sands National Park, New Mexico, USA
Vast dunes composed of gypsum sand, formed from the erosion of gypsum deposits in the Tularosa Basin.
Utah, USA
Significant deposits of gypsum, particularly in the Great Salt Lake region and other evaporite basins.
Nova Scotia, Canada
Large gypsum deposits, particularly in the Windsor Group, are extensively mined.
Spain
Historically significant alabaster quarries and various gypsum occurrences.
Australia
Extensive gypsum deposits, including large 'desert rose' formations.
Collecting tips
- Look for Evaporite Environments. Gypsum is common in sedimentary basins where ancient seas or lakes evaporated, often alongside other evaporite minerals like halite and anhydrite.
- Check for Softness. Gypsum is very soft (Mohs hardness 2). It can be easily scratched with a fingernail, which helps distinguish it from harder minerals like calcite.
- Observe Cleavage. Look for its perfect cleavage, especially in selenite varieties, which can be peeled into thin, flexible sheets.
- Identify Crystal Habits. Recognize the different forms: clear, tabular selenite; fibrous, silky satin spar; or massive, fine-grained alabaster.
- Consider Hydration. In some areas, gypsum forms from the hydration of anhydrite, so look for it in proximity to anhydrite deposits, especially where groundwater is present.
Quick Check
- Color:
- Colorless to white (most common), but can be tinted by impurities.
- Luster:
- Vitreous, pearly, or silky.
- Streak:
- White
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