McAfee SECURE sites help keep you safe from identity theft, credit card fraud, spyware, spam, viruses and online scams

Home » Gemstones » Aventurine


Aventurine

A translucent quartz with sparkling reflections that occurs in a range of colors.




What is Aventurine?



Aventurine is a variety of translucent quartz with abundant small plate- or flake-shaped inclusions. Light entering the quartz strikes these inclusions and reflects from them. This produces a sparkly appearance known as “aventurescence”. When the inclusions are abundant and in a common orientation their reflections are eye-catching. This is what gives aventurine its appeal as a gemstone. Aventurine is usually green, but also occurs in orange, yellow, red, pink, brown, white, and blue.


Types of Inclusions



The most common inclusion in aventurine is fuchsite, a green chromium-rich mica. It can be abundant enough in the quartz to give the material a green color. Some people think that aventurine should be classified as a rock because the inclusions often make up ten to twenty percent of the material.

Small reflective particles of other materials can cause aventurescence in quartz. Hematite and goethite can produce pink, orange, red, and brown aventurine. Muscovite and ilmenite can produce blue, gray or white aventurine. Bright reflections and attractive colors make aventurine a popular semi precious gemstone.


Physical Properties of Aventurine



Aventurine has most of the properties of quartz, its dominant ingredient. The presence of inclusions give quartz its aventurescence and alter some of its other properties.

Aventurine has a hardness of about 6 1/2 instead of the 7 of quartz. The most common mineral inclusions associated with aventurine all have a hardness lower than quartz. This is thought to weaken the material and result in a lower hardness.

Many of the common aventurine inclusions have a specific gravity that is higher than quartz. If abundant, inclusions such as hematite, ilmenite and goethite should give aventurine a specific gravity higher than quartz.


Physical Properties of Aventurine

Chemical Classification Silicate - SiO2
Color Usually green. Also orange, yellow, red, pink, white, brown, and blue.
Streak Colorless (harder than the streak plate).
Luster Vitreous, aventurescent.
Diaphaneity Translucent to nearly opaque.
Cleavage None, conchoidal fracture.
Mohs Hardness 6.5 to 7
Specific Gravity 2.6 to 2.7 (higher when heavily included)
Diagnostic Properties Aventurescence, usually green, hardness, conchoidal fracture.
Chemical Composition SiO2
Crystal System hexagonal
Uses Gemstone, small sculptures, utility items.


Uses of Aventurine



Green aventurine is a common material used to produce beads and cabochons. Other colors are used but because they are usually less than highly attractive they are not seen as often. Earrings, pendants, rings, and other jewelry are made from green aventurine.

Aventurine is sometimes used to make bowls, vases and small sculptures. Green aventurine is a less expensive and popular alternative substitute for jade and amazonite. Some buyers simply want an attractive green stone and the flash of aventurine suits them.

Aventurine is an inexpensive and popular material for making tumbled stones in a rock tumbler. If the mica particles are small it can produce a smooth finish. Beginners can be successful tumbling fine-grained aventurine. Coarse mica particles tend to pluck out, giving the polished stones a pitted appearance. Aluminum oxide, cerium oxide and tin oxide will all produce a polish on aventurine.


Sources of Aventurine



Small amounts of aventurine occur in many parts of the world. India is by far the most important commercial producer of aventurine. Brazil is the second place producer. Russia, Spain, Austria and Tanzania produce smaller amounts of aventurine.

Some people hold the opinion that most of the aventurine sold today has inadequate aventurescence to merit the name. Immediately discernable aventurescence is unusual to find and remarkable aventurescence is extremely rare.


More About Aventurescence



The phenomenon of aventurescence is not confined to quartz. Oligoclase and plagioclase feldspars sometimes contain inclusions of hematite or copper that produce aventurescence. These are known as "aventurescent feldspar" or by the more popular name of “Sunstone”.

The name "aventurine" originated in the 1600s when Italian glass makers blended tiny particles of copper into a batch of molten glass. The result was a sparkly glass that they named "avventura" or, in English, "by chance".

Similar materials are still made today. Two of these products are "aventurine glass" and "goldstone". These commercial stones can be recognized because the coarse metal flakes are visible in the transparent glass. Sometimes blue or green "goldstone" is made by starting with a colored glass.


Last modified: July 2015

Contributor:


Find it on Geology.com




More from Geology.com


Minerals
Minerals: Information about ore minerals, gem materials and rock-forming minerals.
Gemstones
Gemstones: Fantastic images and articles about colored stones and diamonds.
Find Minerals & Gems: Dozens of sites where you can dig and keep what you find.
Yosemite Glaciers
Yosemite Glaciers: There are two active glaciers in Yosemite - but they are slowly melting away.
What is a Maar?
What is a Maar? The second most common volcanic landscape feature on Earth.
The Largest Tsunami!
The Largest Tsunami! The tsunami with the highest run-up was in Lituya Bay, Alaska.
Kyanite
Kyanite is a metamorphic mineral that sometimes has a gemmy transparent blue color.
oil fields at night
Oil from Space at Night These night views of Earth show oil field illumination and gas flaring.


green aventurine
A small polished piece of aventurine about three centimeters across that shows the translucence, highly included nature and aventurescence of the material. The green inclusions in the stone are fuchsite, a green, chromium-rich mica similar to muscovite.




blue aventurine
A blue specimen of aventurescent quartz from India. This specimen is about ten centimeters across.


light green aventurine cabochon
A brightly polished cabochon cut from a piece of light green aventurine.


green aventurine tumbled stones
A brightly polished cabochon cut from a piece of light green aventurine.


More Gemstones
  Aventurine
  Polka Dot Agate
  100+ Gems
  Bloodstone
  Tanzanite
  Extraterrestrial Gems
  Pictures of Opal
  Emerald


© 2005-2015 Geology.com. All Rights Reserved.
Images, code and content of this website are property of Geology.com. Use without permission is prohibited. Pages on this site are protected by Copyscape.