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: Citrine

Citrine Gemstones used in Jewelry

Source: Brazil, India, Madagascar, Sri Lanka

Birthstone: November (Alternate: Topaz)

The name "Citrine" (Citrin German, Topacio falso Spanish, Citrino Italian) comes from the French word "citron," or "lemon," for its yellow color. Citrine closely resembles topaz (also a birthstone for November), but is slightly softer, and has less brilliance. Citrine has been used in Greece since the Hellenistic period, from the end of the 4th to the end of the 1st century BC.

Primary sources for citrine are found in Brazil, Madagascar, and Sri Lanka. Citrine is a coarse-grained, transparent variety of the tectosilicate silica mineral quartz. The yellow color in natural citrine is derived from the presence of iron. Typically, the darker the color of the citrine, the higher the grade. Cryptocrystalline varieties of citrine can be multicolored.

Naturally occurring citrine derives its golden color from the presence of iron (Fe³) ions. Purple amethyst will turn to citrine when heated in a kiln for a certain period of time and much of the yellow, gold, or orange citrine on the market today is heat-treated amethyst.

Citrine (Quartz) Crystallography, Chemistry, Physical Properties

Crystal System	trigonal, hexagonal (trigonal-trapezohedral)
Crystal Habit	enantiomorphic, prismatic
Specific gravity (SG)	2.65
Mohs Hardness Scale	7.0 to 7.5
Toughness	good
Fracture	conchoidal
Cleavage	weak in three directions
Streak	white
Chemical Composition	SiO₂ (quartz: silicon dioxide)

Citrine (Quartz) Optical Properties

Optical Properties	double refractive
Refractive Index	1.544 to 1.553
Birefringence	+0.009 (B-G interval)
Pleochroism/Dichroism	weak dichroism
Surface Luster	vitreous (glassy)
Diaphaneity	transparent, translucent
Gem Color	brown, orangy-yellow, yellow

Most Citrine sold today started out as an orange-brown variety of Amethyst. Citrine is heat-treated to produce the pale-yellow or golden color that is characteristic of the stone, and citrine can permanently change color if left in direct sunlight for several hours.

Folklore surrounding citrine: In ancient times, citrine was carried as a protection against snake venom. It is also thought to aid digestion, and remove toxins from the body.

Synthetic Citrine

Synthetic citrine has many of the same physical properties as its natural counterpart, making identification difficult. Artificial or "lab-grown" citrine is created by growing quartz crystals in a hydrothermal solution, in a pressure vessel known as an autoclave. By exerting varying pressure and/or temperature in the different areas of the autoclave, a feed material (lascas) dissolves in the hotter zone and is redeposited onto seed crystals which are located in the cooler zone; thereby forming synthetic quartz crystals [2]. The entire growth process takes between 30 to 60 days.

Synthetic citrine is often free of inclusions, but may show some evidence of hydrothermal growth in the form of inclusions resembling breadcrumbs which are aligned perpendicular to the seed plate. It might also have color banding that is parallel to the seed plate. Additionally, synthetic citrine should lack the 'Brazil-law' twinning which is observed in natural gems.

Bibliography and Reference on Ametrine

1. Judith Crowe, The Jeweler's Directory of Gemstones . DK Publishing.

2. GIA, Characteristics of Citrine, Ametrine & Smoky Quartz www.gia.edu

3. ICA, Ametrine: Spinning purple into gold . www.gemstone.org

4. Caltech, Ametrine . minerals.caltech.edu

5. Renee Newman, Gemstone Buying Guide . International Jewelry Publications; 2nd edition

6. Antoinette L . Matlins, Antonio C. Bonanno, Gem Identification Made Easy . Gemstone Press

7. A.C. Akhavan, Twinning in Quartz Crystals www.quartzpage.de

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