Yellow Calcite
Calcite var. Yellow Calcite · Semi-Precious Gemstone / Mineral Specimen
Crystal System
Trigonal - Hexagonal Scalenohedral; This specimen is tumble-polished and lacks visible crystal faces, but typically occurs as rhombohedrons, scalenohedrons, or massive forms.
Mineral Group
Carbonates (Calcite Group)
Chemical Formula
CaCO3 (Calcium Carbonate with trace Iron or Sulfur)
Formation Process
Sedimentary precipitation or Hydrothermal. Forms typically from evaporation in marine environments or from mineral-rich hot springs at relatively low temperatures.
About This Crystal
A tumble-polished, semi-translucent yellow stone with a waxy to vitreous luster. Features subtle cloudy white inclusions and internal fractures typical of carbonates. The color ranges from a pale lemon to a deep honey yellow depending on iron concentration.
Physical Characteristics
Color: Yellow to Golden; Streak: White; Cleavage: Perfect rhombohedral in three directions (not visible due to polish); Fracture: Conchoidal to uneven; Specific Gravity: 2.71; Fluorescence: Often fluoresces pink or orange under Longwave UV.
Optical Properties
Refractive Index: 1.486 - 1.658; Birefringence: Extremely high (0.172); typically doubly refractive (uniaxial negative). This specimen displays a characteristic 'waxy' glow when light penetrates the surface.
Hardness & Durability
Origin Region
Mexico (notably Chihuahua and Durango), Brazil, and USA; forms in sedimentary limestone environments and hydrothermal veins.
Hardness & Durability
Mohs Hardness: 3.0; very soft and susceptible to scratching. Brittle tenacity. It is easily damaged by household dust (which contains quartz) and should not be used in high-wear jewelry.
Care & Maintenance
Clean only with warm soapy water and a soft cloth. Avoid ultrasonic cleaners, steam, and all acids (even lemon juice or vinegar) which will dissolve the stone. Store separately from harder stones to prevent scratching.
Rarity & Value
Common; very affordable. Value is determined by color intensity and translucency. Large polished tumbles are widely available; heat treatment is rare but dyeing is occasionally used for deeper shades.
Special Characteristics
Displays strong double refraction if transparent (iceland spar effect). This tumble may show faint internal 'veiling' or phantom-like wisps due to its carbonate structure.
Lore & History
Historically used in various cultures as a stone of the sun. In modern gemstone lore, it is associated with the Solar Plexus chakra and believed to enhance personal will, self-confidence, and mental clarity.