Moonstone
Orthoclase Feldspar var. Moonstone · Semi-Precious Gemstone
Crystal System
Monoclinic; often found as tumbled pebbles or massive forms showing schiller
Mineral Group
Silicates (Tectosilicate), Feldspar Group
Chemical Formula
(K,Na)AlSi3O8
Formation Process
Forms through slow cooling of magma, where orthoclase and albite separate into microscopic alternating layers, causing light interference.
About This Crystal
This specimen is a tumbled white to light gray stone with a pearly to vitreous luster. It exhibits characteristic translucency and internal light scattering. The surface shows some grayish-black inclusions typical of low-grade feldspar specimens.
Physical Characteristics
Color: White to gray; Streak: White; Cleavage: Two directions at nearly 90 degrees; Fracture: Conchoidal to uneven; Specific Gravity: 2.56-2.59; Fluorescence: Weak bluish or orange under UV light.
Optical Properties
Displays adularescence (a milky blue or white glow caused by light diffraction between layers). Refractive Index: 1.518-1.526; Birefringence: 0.005-0.008; Doubly refractive.
Hardness & Durability
Origin Region
Notable sources include Sri Lanka (blue sheen), India (rainbow varieties), Madagascar, and Myanmar. Formed in pegmatites and metamorphic rocks.
Hardness & Durability
Mohs Hardness: 6.0-6.5. Fair toughness but prone to cleavage cracks; moderate durability for jewelry (best in pendants or earrings).
Care & Maintenance
Clean with warm soapy water and a soft brush. Avoid ultrasonic and steam cleaners. Sensitive to sudden temperature changes and pressure.
Rarity & Value
Common in many varieties; fine-quality colorless specimens with strong blue adularescence are rare. Inexpensive in tumbled form ($1-$10).
Special Characteristics
Adularescence (the 'inner glow' effect). Some specimens show chatoyancy or four-rayed asterism. Inclusions may include 'centipedes' (tiny stress cracks).
Lore & History
Historically used in Roman jewelry and linked to lunar deities. In folklore, it was believed to be made of solidified moonlight. Traditionally associated with the Crown and Third Eye chakras, used for intuition and emotional balance.