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Roger Weller, geology instructor                                     

wellerr@cochise.edu
Quartz Family Gemstones-by Audrey LaClair
                            
                          Citrine

Citrine is referred to as any cluster or quartz crystal that is yellow or orange in color.  It gets it's name from the French word citron, which means lemon.  And since it usually has a lemon color, it was named citrine.

photo by R.Weller

Most citrine is amethyst or smoky quartz that has been exposed to extreme heat.  If amethyst or smoky quartz is exposed long enough, it will turn a yellow color.  But often a synthetically heated quartz will have orange or reddish tints, unlike natural citrine which is a pale yellow.  It is rare to find natural citrine, because most is heat treated.  Because it is so readily available, it is relatively inexpensive. 

"Citrine is recognized by its color, crystal habit, occurrence, hardness, glassy luster, conchoidal fracture and lack of cleavage"
http://www.mineralminers.com/html/citminfo.htm
 

Most citrine is mined in Brazil, but it can also be found in Spain, the former USSR, and Madagascar.  In the USA it is found in Colorado, California, Georgia, and Nevada.

photo by R.Weller

PHYSICAL PROPERTIES
 

·        Citrine Chemical composition: SiO₂ (minor Fe³⁺ impurities cause citrine's color)

·        Class: tectosilicate

·        Crystal system: Hexagonal-R; 32 (trigonal-trapezohedral)

·        Crystal habit: Macroscopic crystals occur as horizontally striated hexagonal prisms terminated by a combination of positive and negative rhombohedrons forming six sided pyramids. Citrine also occurs as drusy masses showing only the rhobohedral terminations. It can also be massive.

·        Twinning: Dauphine twin with c the twin axis, Brazil twin with {1120} the twin plane

·        Specific gravity: 2.65

·        Index of refraction: 1.54-1.55

·        Birefringence: 0.009

·        Pleochroism: perceptible

·        Hardness: 7

·        Color: shades of yellow to reddish-orange

·        Luster: vitreous

·        Transparency: transparent to translucent

·        Cleavage: none

·        Fracture: conchoidal

·        Streak: white

From (http://www.mineralminers.com/html/citminfo.htm)
 

References:

http://www.mineralminers.com/html/citminfo.htm
http://www.gemstone.org/gem-by-gem/english/citrine.html
http://mineral.galleries.com/minerals/gemstone/citrine/citrine.htm
http://www.jewelrymall.com/stones/citrine.html
http://www.jewelrymall.com/stones/citrine.html