Quartz

Posted by Elisabeth Dignan on

 

Welcome to my new mineral series! This blog post is the first of a series of posts I'll be making, going in depth about some minerals you may see used in jewelry (and possibly some interesting ones that aren't used in jewelry as well). I make jewelry because I love gemstones, and hopefully this series will help spread the love!

 

Where better to start than quartz?

 

 

Quartz is a silicon dioxide (SiO2). It is a 7 on the Mohs scale of hardness. Its’ crystal system is trigonal, meaning it can form hexagonal (six-sided) prisms, but it doesn’t always.

 

Many stones (besides the obvious) you might be familiar with are varieties of quartz. Amethyst, citrine, prasiolite (which often goes by the misnomer “green amethyst”), Herkimer “diamonds,” and chalcedony (such as carnelian, tiger’s eye, onyx, jasper and agate) are all types of quartz.

 

There are two types of quartz: crystalline and microcrystalline. Amethyst, citrine, prasiolite, smoky quartz, and rose quartz are examples of the crystalline variety. Chalcedony (and therefore all of its’ varieties) is microcrystalline.

  

Colorless natural quartz is called “rock crystal.” It can be transparent to opaque. Ice-clear quartz was called “krystallos” (hence, “crystal”) by the ancient Greeks. The word “quartz” comes from the German “quarz.”

 

Quartz is the second must abundant mineral, after feldspar (labradorite and rainbow moonstone are feldspar). It makes up about 12% of the earth’s crust.

 

Quartz can contain inclusions that add to its’ beauty. Iron oxides like hematite, goethite, and cacoxenite are common in quartz (“lepidocrocite,” “Super Seven”), as is black tourmaline (tourmalated quartz), and rutile (rutilated quartz).

*An interesting note about “lepidocrocite” – I can find no legitimate evidence that the mineral lepidocrocite has ever actually been found in quartz. It is speculated by professionals that the material thought to be lepidocrocite in quartz specimens is actually other iron oxides like hematite or goethite. Therefore, "lepidocrocite" is a misnormer, despite being so commonly used for included quartz.

 

Treatments: quartz is often treated to change its appearance. The colors of amethyst, citrine, prasiolite, and smoky quartz are often produced or enhanced by irradiation or heating. “Aura quartz” is coated with metal (such as titanium) by placing the quartz in a vacuum chamber and adding a metal vapor, in a process called “vapor deposition.”

 

What to be wary of: If you're after natural stones, look out for “fruit quartz.” Most strawberry quartz, pineapple quartz, blueberry quartz etc. is just fancy glass. Also watch out for “hydroquartz,” which is a man-made glass material. It is NOT the same as “synthetic” quartz – which has the same chemical composition as natural quartz. Most bright colored “quartz” beads are hydroquartz and may go by names like “paraiba quartz,” "London blue quartz," "emerald quartz" etc., based on the gem they are imitating  – these names are considered misleading by the GIA and should not be used. These beads should be disclosed to be imitation quartz. Color names like "magenta quartz" are misleading as well, when the material is hydroquartz, since the material is not natural quartz. 

 

Thanks for reading! I will get into more detail about individual varieties of quartz in future posts. Some of these will be rose quartz, smoky quartz, Herkimer diamonds, amethyst etc. I hope you learned something new and enjoyed reading about quartz!

 

 

Much of the information in this post came from my personal knowledge from years of reading and learning about minerals. Whenever I’m looking to verify information or learn something new, I use these validated websites:

 

www.mindat.org

www.gemdat.org

www.gia.edu

www.minerals.net

www.geology.com

www.mineralseducationcoalition.org