trigonal Tectosilicates
Citrine
Formula SiO2:Fe
Crystal Structure
#! Species: Citrine (Quartz)
#! System: Trigonal (32)
#! Habit: Prismatic with sector colour zoning
trigonal[32]:{10-10}@0.5 + {10-11}@1.2[colour_zone:sector] + {01-11}@1.0 | elongate(c:2.0)
trigonal
32
{10-10} {10-11} {01-11}
Quick Facts
Hardness
7.0
Specific Gravity
2.65
Refractive Index
1.544
Optical Character
Uniaxial +
Physical Properties
- Crystal System
- trigonal
- Hardness (Mohs)
- 7.0
- Specific Gravity
- 2.65
- Cleavage
- None
- Fracture
- Conchoidal
- Lustre
- Vitreous
Optical Properties
- Refractive Index
- 1.544
- Birefringence
- 0.009
- Optical Character
- Uniaxial +
- Dispersion
- 0.013
- Pleochroism
- weak: Yellow / Paler yellow (Subtle dichroism; rarely visible in pale material)
Characteristics
Colours
Pale yellowGolden yellowOrangeMadeira (brownish-orange)Honey
Localities
BrazilBoliviaMadagascarSpainRussia
Common Inclusions
Two-phase fluid inclusionsNegative crystalsColour zoning (often absent in heated material)Brazil-law twinning (in natural)
Known Treatments
Heat treatment (from amethyst - most common)IrradiationNone (rare natural citrine)
Crystal Forms
prismrhombohedron
Notes
Most commercial citrine is heat-treated amethyst; natural citrine is rare and typically pale yellow
Related Minerals
Other minerals in the trigonal system
