Calcite
Calcite var. Spar · Mineral Specimen / Industrial Mineral
Crystal System
Trigonal; often occurs in rhombohedral, scalenohedral, or massive habits in limestone.
Mineral Group
Carbonates
Chemical Formula
CaCO3
Formation Process
Primarily sedimentary through chemical precipitation or biogenic accumulation; also hydrothermal and metamorphic.
About This Crystal
Colorless to white translucent crystals embedded in a brown, earthy matrix. Exhibits a vitreous luster and characteristic rhombohedral cleavage visible on broken surfaces.
Physical Characteristics
Color: White/Colorless; Streak: White; Cleavage: Perfect rhombohedral in three directions; Fracture: Conchoidal; Hardness: 3; Specific Gravity: 2.71; often strongly fluorescent under UV light.
Optical Properties
High birefringence (double refraction); Refractive Index: 1.486 - 1.658; Uniaxial negative.
Hardness & Durability
Origin Region
Found globally; common in Iceland (Iceland Spar), Mexico, and the USA. This specimen appears to be from a sedimentary limestone or metamorphic marble environment.
Hardness & Durability
Mohs hardness of 3; very brittle and soft. Not suitable for regular jewelry wear as it scratches easily and reacts to acids.
Care & Maintenance
Avoid all acids (even vinegar), cleaners, and ultrasonic tools. Clean with a dry or slightly damp soft cloth. Store separately from harder minerals.
Rarity & Value
Very common mineral; value for this specific specimen is low (field collector value), primarily dependent on crystal clarity and form.
Special Characteristics
Strong acid reaction (effervescence with HCl); notable double refraction (doubling of text viewed through clear crystals).
Lore & History
Historically used in optics (Vikings potentially used Iceland Spar for navigation). In lore, it is believed to be a stone of amplification and cleansing, traditionally associated with the Crown Chakra.