Introduction
Selenite is a beautiful mineral and has metaphysical properties but it’s also got some interesting science behind it. This blog will go into the geological formation, physical properties and chemical properties of selenite so you can get a full understanding of this amazing crystal from a scientific perspective.
What is Selenite?
Selenite is a crystalline form of the mineral gypsum, chemically known as calcium sulfate dihydrate (CaSO₄·2H₂O). Its name comes from the Greek word selēnē meaning moon, because of its moon like glow.
Characteristics
- Color: Translucent or white, can appear orange, green, blue or brown.
- Luster: Pearly or vitreous.
- Hardness: Very soft, 2 on the Mohs scale.
- Cleavage: Perfect, can split into thin sheets.
Geological Formation of Selenite
Selenite forms in sedimentary environments, in evaporative environments where water bodies dry up and leave behind mineral deposits.
Formation Process
- Evaporation: When saline water bodies evaporate they concentrate minerals like calcium and sulfate.
- Crystallization: Over time these minerals combine and crystallize to form gypsum, including its crystalline form selenite.
Found In
- Worldwide, with large deposits in:
- Naica, Mexico: Home to the Cave of Crystals, has some of the largest selenite crystals ever found.
- Morocco: High quality peach and white selenite.
- United States: Found in Utah and Oklahoma.
Physical Properties of Selenite
1. Softness
- Selenite is very soft and can be scratched with your fingernail.
- Its softness makes it prone to chipping and requires care.
2. Transparency
- Its translucency is due to its crystalline structure which allows light to pass through partially.
3. Cleavage
- Perfect cleavage allows selenite to split into thin sheets, used in industrial applications.
4. Solubility
- Selenite is water soluble, prolonged exposure to moisture will dissolve it.
Chemical Composition of Selenite
| Element | Percentage Composition |
| Calcium (Ca) | ~23.3% |
| Sulfur (S) | ~18.6% |
| Oxygen (O) | ~56.1% |
| Water (H₂O) | ~2 molecules per formula |
The presence of water molecules in its structure gives selenite its dihydrate classification and contributes to its softness and solubility.
Selenite Types
1. Clear Selenite
- Glass like transparency and high vibration.
- Used in metaphysical practices and decorative pieces.
2. Satin Spar
- Fibrous, silky texture and pearly sheen.
- Often mistaken for selenite but same chemical composition.
3. Desert Rose
- Formed by wind and sand erosion, petal like formations.
4. Peach Selenite
- Coloured by iron inclusions, often associated with grounding energy.
Scientific Uses of Selenite
1. Soil Amendment
- Gypsum (including selenite) is used to improve soil structure and reduce salinity in agricultural fields.
2. Industrial Applications
- Used in cement, plaster and wallboard production.
3. Optical Applications
- Thin sheets of selenite have been used in polarizing microscopes due to its optical properties.
Notable Selenite Formations
1. Cave of Crystals (Naica, Mexico)
- Has massive selenite crystals, some over 12 meters long and several tons heavy.
- Formed over thousands of years in a high humidity environment saturated with calcium sulfate.
2. Selenite Hill (Oklahoma, USA)
- A popular digging and collecting site for selenite crystals, known for its “hourglass” inclusions.
Selenite and Earth’s History
Selenite deposits tell us:
- Past Climate: Indicates periods of heavy evaporation and arid conditions.
- Water Chemistry: Reveals the composition of ancient saline water bodies.
How to Care for Selenite: A Scientific Perspective
1. No Water
- Water will dissolve the crystal due to its solubility. Keep selenite dry always.
2. Handle with Care
- Soft and has perfect cleavage. Handle gently to avoid scratches or breakage.
3. Storage
- Store in a stable environment, away from direct sunlight or humidity to preserve its structure and appearance.
Selenite vs Other Gypsum Varieties
| Property | Selenite | Alabaster | Satin Spar |
| Appearance | Transparent, striated | Opaque, fine-grained | Fibrous, silky texture |
| Primary Use | Energy work, décor | Sculpting, carving | Decorative, metaphysical |
| Hardness | 2 | 2 | 2 |
Selenite FAQs
1. Is Selenite found in all Gypsum deposits?
No, selenite forms when gypsum crystals have space to grow without interference.
2. Why is Selenite so soft?
Due to its layered structure and water molecules in its composition.
3. How long does it take to form?
From hundreds to thousands of years depending on the environment.
4. Can Selenite be used in jewelry?
Yes but handle with care.
Conclusion
Selenite benefits is not just a metaphysical crystal but a geological wonder that tells us about the Earth’s natural world. Its formation, properties and uses are worth studying for scientists and crystal lovers. Now you know the science behind selenite.
