Home
>
The Crystal and Mineral Vault
>
Selenite Crystal Properties Formation and Mineralogical Profile
Selenite Crystal Properties Formation and Mineralogical Profile
by Laura Konst
Selenite
Pronunciation: Si luh nait
Mineral Group: Sulphates
Mineral Category: Hydrated Gypsum
Chemical Formula: CaSO₄ · 2H₂O
Selenite is a crystalline variety of gypsum recognised for its translucency fibrous structure and distinctive luminous appearance. It forms through the slow evaporation of mineral rich saltwater environments where calcium sulphate crystallises into elongated blades plates or fibrous aggregates.
One of the most visually striking occurrences of Selenite is found in the Cave of the Crystals, often referred to as the Cave of Swords where enormous gypsum crystals developed under highly specific geological conditions of heat humidity and mineral saturation.
Geological Formation and Structure
Selenite forms in evaporitic environments where seawater or saline lakes gradually evaporate leaving behind sulphate rich mineral deposits. Over time these conditions allow gypsum crystals to grow in layered fibrous or tabular forms.
Its internal structure is responsible for its soft flexible nature and its ability to transmit light giving Selenite its characteristic glow. Unlike harder silicate minerals Selenite is relatively delicate and must be handled with care.
Physical and Optical Properties
Mohs Hardness: 2
Crystal System: Monoclinic
Cleavage: Perfect in one direction
Fracture: Splintery fibrous
Tenacity: Flexible sectile
Refractive Index: 1.520 to 1.530
Specific Gravity: 2.31
Birefringence: 0.010
Pleochroism: None
Selenite displays excellent cleavage which allows it to split cleanly into thin sheets. This property historically made gypsum varieties useful for early window panes and light diffusing architectural elements.
Colour Variations
Selenite occurs in a range of natural colours depending on trace inclusions and formation conditions including
• Clear and colourless
• White and milky
• Grey
• Green
• Orange
• Brown
Colour variations are typically caused by clay mineral inclusions iron oxides or organic material present during crystal growth.
Historical and Cultural Context
The name Selenite originates from the Greek word selēnē meaning moon referencing its soft reflective appearance. Ancient cultures associated the mineral with lunar symbolism clarity and illumination often using it in sacred spaces and spiritual architecture.
Historically gypsum minerals have been used for ornamental carving plaster production and early construction materials due to their abundance and workable softness.
Metaphysical Associations
While this profile focuses on mineralogical properties Selenite has long been referenced in metaphysical traditions.
Chakras: Crown and Third Eye
Zodiac: Taurus
Element: Air
Planetary Association: Moon
Selenite is traditionally associated with clarity purification and heightened awareness. Its symbolism is closely tied to light reflection and mental focus rather than physical interaction.
Affirmation:
I am a vessel of pure light connecting with wisdom within and around me.
Use and Care
Due to its softness and solubility Selenite should never be cleansed with water.
Care recommendations:
• Keep dry and away from moisture
• Clean gently with a soft dry cloth
• Store separately to avoid scratching
Selenite is often placed near other mineral specimens or within display environments where its visual clarity and form can be appreciated without physical handling.
Mineral Vault Notes
Selenite remains one of the most recognisable and visually distinctive gypsum minerals. Its geological formation optical properties and historical significance make it an essential inclusion in any mineral collection whether studied for its crystallography evaporite formation or cultural symbolism.
Its combination of softness translucency and scale from small blades to monumental formations continues to fascinate collectors mineralogists and educators alike.
If you would like help exploring different crystals or minerals, feel free to get in touch and we will be happy to share general guidance and information.
Contact us here
Love, Laura
Related Reading
Share
