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Citrine is a macrocrystalline variety of quartz, characterized by its transparent to translucent yellow, orange, or brownish-orange color. It is a durable mineral, making it suitable for various applications, particularly in jewelry. Its color can range from pale yellow to a deep reddish-orange, with the darker, more saturated colors often being more highly valued. The term 'citrine' is derived from the Old French word 'citrin', meaning 'yellow', which in turn comes from the Latin 'citrus'.
How to Identify
- Color
- Ranges from pale yellow to golden yellow, orange-yellow, and reddish-brown. The color is typically uniform throughout the crystal.
- Luster
- Vitreous (glassy).
- Texture
- Smooth to conchoidal fracture surfaces.
- Crystal Form
- Typically occurs as prismatic hexagonal crystals with pyramidal terminations. Can also be found in massive or granular forms.
- Cleavage
- None. Quartz lacks cleavage.
- Geological Environment
- Found in igneous rocks (especially granites and pegmatites), metamorphic rocks, and hydrothermal veins. Often occurs in geodes and alluvial deposits.
Key Facts
- Hardness: 7 on the Mohs scale
- Specific Gravity: 2.65 g/cm³
- Crystal System: Trigonal
- Color: Yellow, golden yellow, orange-yellow, reddish-brown
- Luster: Vitreous
- Transparency: Transparent to translucent
- Fracture: Conchoidal
- Cleavage: None
- Composition: Silicon Dioxide (SiO2)
Quick Check
- Color: Yellow to orange-brown
- Luster: Vitreous
- Streak: White
Physical Characteristics
- Crystal Habit: Prismatic hexagonal crystals, often terminated by rhombohedral faces; also massive, granular, cryptocrystalline.
- Cleavage Type: None (lacks cleavage)
- Fracture Type: Conchoidal
- Tenacity: Brittle
- Luster Type: Vitreous (glassy)
Formation
Citrine is a variety of quartz, a tectosilicate mineral. Its characteristic yellow to orange-brown color is primarily due to trace amounts of ferric iron (Fe3+) impurities within the crystal lattice. Natural citrine is relatively rare. Most commercially available citrine is produced by heat-treating amethyst or smoky quartz. When amethyst (purple quartz, colored by irradiation-induced color centers involving iron impurities) is heated to temperatures typically between 450°C and 550°C, the iron impurities undergo a change in oxidation state and/or coordination, resulting in the yellow to orange coloration. Similarly, some smoky quartz, which owes its color to natural irradiation, can also be heat-treated to produce citrine. The formation of natural citrine occurs in hydrothermal veins, pegmatites, and certain igneous rocks where conditions allow for the incorporation of iron during quartz crystallization and subsequent natural irradiation and/or heating.
Usage
Citrine is primarily used as a gemstone in jewelry due to its attractive color and durability. It is cut into various shapes, including faceted stones, cabochons, and beads. Larger specimens are also used for ornamental carvings and as display pieces for mineral collectors. In metaphysical practices, it is often associated with prosperity and positive energy.
Age Distribution
Citrine forms in various geological settings and is not restricted to a specific geological age. Its formation is tied to the crystallization of quartz in hydrothermal veins, pegmatites, and igneous rocks, which can occur across vast geological timescales from Precambrian to Cenozoic.
Where to Find
Brazil
The primary source of both natural and heat-treated citrine, particularly from the states of Rio Grande do Sul and Minas Gerais. Many large amethyst geodes are heat-treated here to produce citrine.
Madagascar
Known for producing natural citrine, often with a desirable golden-orange hue.
Uruguay
A significant source of amethyst, much of which is heat-treated to become citrine.
Russia (Ural Mountains)
Historically a source of natural citrine.
France
Some natural citrine occurrences, particularly in the Dauphiné Alps.
Spain
Known for some natural citrine deposits.
Scotland
Historically, a source of 'Cairngorm' quartz, which includes smoky quartz and some citrine.
Finding Tips
Look for Quartz Environments
Citrine, being a variety of quartz, will be found in geological environments conducive to quartz formation, such as pegmatites, hydrothermal veins, and igneous rock cavities (geodes).
Examine Color and Clarity
Natural citrine often has a paler, more subtle yellow color compared to heat-treated amethyst, which can exhibit a reddish-orange tint and sometimes show faint banding or 'zebra stripes' from the original amethyst growth patterns. Look for good transparency and minimal inclusions.
Check for Crystal Habits
Search for well-formed hexagonal prismatic crystals with pyramidal terminations, or crystalline masses within rock matrices.
Distinguish from Topaz
While similar in color, topaz is significantly harder (8 on Mohs scale) and has perfect basal cleavage, unlike citrine (quartz), which has no cleavage and a Mohs hardness of 7.
Be Aware of Heat Treatment
Most citrine on the market is heat-treated amethyst. While still chemically SiO2, it's important for collectors to understand this distinction. Natural citrine is rarer and often commands a higher price.
Similar Rocks
Yellow Topaz
Al2SiO4(F,OH)2
Also known as: Imperial Topaz (for orange-pink varieties)
Golden Beryl
Be3Al2Si6O18
Also known as: Heliodor
Smoky Quartz
SiO2
Also known as: Morion (for very dark varieties)
Amethyst
SiO2
Also known as: Purple Quartz
Scientific Classification
- Mineral Class
- Silicates
- Group
- Tectosilicates (Quartz Group)
- Crystal System
- Trigonal (or Hexagonal-Rhombohedral)
- Chemical Formula
- SiO2
- Composition
- Silicon Dioxide
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