Where is Selenite found?
Selenite (a variety of Gypsum)
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Open the appSelenite 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 Selenite
Naica Mine, Chihuahua, Mexico
Famous for its 'Cave of the Crystals' (Cueva de los Cristales), containing some of the largest selenite crystals ever discovered, reaching up to 12 meters (39 feet) in length.
Oklahoma, USA
Known for its 'Great Salt Plains' where 'hourglass selenite' crystals form, characterized by sand inclusions that create an hourglass shape within the crystal.
Utah, USA
Various locations produce selenite, including 'desert roses' and clear crystals.
Australia
Significant deposits of selenite and other gypsum varieties are found, particularly in arid and semi-arid regions.
Spain
Historically important source of 'lapis specularis' (transparent selenite) used by the Romans. Modern deposits are also found.
Morocco
A major source of 'desert rose' selenite formations.
Collecting tips
- Look in Evaporite Deposits. Selenite is common in areas where ancient seas or lakes have evaporated, leaving behind sulfate-rich sediments. Look for exposures of shale, limestone, or sandstone in arid regions.
- Check Cave Environments. Caves can provide stable conditions for the growth of large, clear selenite crystals, especially in areas with gypsum-rich bedrock and circulating groundwater.
- Identify Associated Minerals. Selenite often occurs with other evaporite minerals such as halite (rock salt), anhydrite, and sometimes native sulfur. The presence of these minerals can indicate a favorable environment for selenite.
- Test Hardness. Selenite is very soft (Mohs hardness of 2). It can be easily scratched with a fingernail, which helps distinguish it from harder minerals like quartz or calcite.
- Observe Cleavage. Its perfect cleavage into thin, flexible sheets is a key diagnostic feature. Calcite, while also having good cleavage, produces rhombic fragments that are not flexible.
- Consider Crystal Habit. Recognizing the distinct crystal forms like tabular crystals, 'fishtail' twins, 'desert roses,' or fibrous 'satin spar' can aid in identification.
Quick Check
- Color:
- Colorless to white (can be tinted by impurities)
- Luster:
- Vitreous to pearly (silky in satin spar)
- Streak:
- White
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