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: Aventurine Quartzite

Aventurine used in Jewelry

Source: Chile, India, Spain, Russia, USA

Aventurine quartzite is a translucent to opaque, green to bluish-green tectosilicate rock that is a variety of quartz. Aventurine's characteristic glistening or shimmering effect is known as "aventurescence," which is the result of uniformly oriented, platy mineral inclusions within the rock matrix. The name "aventurine" is derived from the Italian name "a ventura" or "by chance."

The presence of fuchsite inclusions, a chrome-bearing variety of muscovite mica, gives aventurine its characteristic silvery greenish-blue sheen. High quantities of fuchsite can cause aventurine to be totally opaque. This macrocrystalline quartz has a massive crystal habit, which is an aggregate of interlocking quartz grains.

Aventurine Necklace by Natalie Baroni

Aventurine Rough

Orange or pinkish-red aventurine quartzite can be confused with aventurine feldspar or sunstone, although aventurine quartzite is more opaque. Aventurine is typically cut into a cabochon or beads. The principal sources for green Aventurine is in the Madras, Mysore, Nadu, or Tamil regions of India. Secondary sources are in the Ural Mountains of Russia, Minas Gerais, Brazil, and Vermont, USA.

Certain varieties of Aventurine can have a brown (pyrite), orange (hematite), or yellowish-orange hue. Sunstone can be confused with orange and red aventurine quartzite (above, right), although sunstone can be more transparent. Aventurine can be noticeably banded, and opaque varieties can be mistaken for malachite.

Aventurine Chemistry & Physical Properties

Crystal System	hexagonal
Crystal Habit	massive
Specific gravity (SG)	2.64 to 2.69
Mohs Hardness Scale	6.5 to 7.0
Toughness	good
Fracture	conchoidal
Cleavage	none
Streak	white
Chemical Composition	K(Al,Cr)₂AlSi₃O₁₀(OH)₂

Aventurine Optical Properties

Optical Properties	singly refractive
Refractive Index	1.50
Birefringence	0.009
Pleochroism	none
Surface Luster	vitreous to dull
Diaphaneity	subtranslucent, opaque
Gem Color	brown, geenish-blue, greenish-gray, bluish-green, pink, white

Aventurine is an inexpensive material for jewelry, and is also used as a landscaping stone, or as an aquarium decoration.

Bibliography and Reference on Aventurine

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

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

3. GIA, Characteristics of Citrine, Amethyst & Smoky Quartz www.gia.edu

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

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

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