Calcite on Matrix
Calcite (var. Iceland Spar or Honey Calcite depending on clarity) · Mineral Specimen / Decorative Stone
Crystal System
Trigonal; commonly occurs in rhombohedral crystals, scalenohedral (dogtooth) forms, or as massive, fibrous, and granular habits as seen in this specimen.
Mineral Group
Carbonates (Calcite Group)
Chemical Formula
CaCO3 (Calcium Carbonate)
Formation Process
Primarily sedimentary through chemical precipitation or biogenic accumulation, but also forms via hydrothermal veins and metamorphic processes (marble formation).
About This Crystal
The specimen features a layer of pale yellow to cream-colored crystalline calcite attached to a dull gray sedimentary rock matrix. The calcite exhibits a fibrous to blocky habit with a vitreous to pearly luster. It is translucent to semi-opaque.
Physical Characteristics
Color: Yellowish-white; Streak: White; Cleavage: Perfect rhombohedral in 3 directions; Fracture: Conchoidal (rarely seen due to perfect cleavage); Specific Gravity: 2.71; Fluorescence: Often shows strong red, pink, or orange under UV light.
Optical Properties
Strongly doubly refractive (birefringence); RI of 1.486–1.658; uniaxial negative; no pleochroism; translucent transparency in this specific piece.
Hardness & Durability
Origin Region
Found globally; notable deposits include Mexico, USA (Tennessee, Missouri), China, and Iceland. Commonly found in sedimentary limestone environments.
Hardness & Durability
Mohs Hardness: 3 (soft, can be scratched by a copper coin). Brittle toughness; low durability for jewelry, highly sensitive to acids.
Care & Maintenance
Avoid all acids (including vinegar), which will dissolve the stone. Clean only with warm soapy water. Store separately from harder stones like quartz to prevent scratches.
Rarity & Value
Common; value for this type of rough specimen is low (Collector/Educational level). Value is based on crystal size and transparency. Unlikely to be treated except for acid washing.
Special Characteristics
Effervesces (fizzes) strongly when in contact with dilute hydrochloric acid. Known for its strong double refraction in clear crystals (Iceland Spar).
Lore & History
Historically used in agricultural lime and early optical instruments. Metaphysically associated with the Solar Plexus chakra, believed to amplify energy and assist in mental clarity and emotional healing.