It is a very complex story to what appears to be a simple gemstone crystal: Quartz. With a chemical equation of SiO2, a silicon dioxide, quartz shares the same basic chemical structure with the window glass of your house. But the simple part of the story ends there, and the really interesting part begins. It is the Story of Quartz and its amazing place in our gemstone jewelry industry.
Seen here, this huge single quartz crystal on a wrought-iron stand demonstrates the enormous sizes possible with quartz crystals, and this one is not that big at 32 inches long when it comes to just how big quartz crystals can grow.
While the full story of quartz could take volumes of newsletters, for our purposes we will talk about quartz as it most impacts our industry. Otherwise, we would be here for hours. The story is that big. Therefore, here is the Story of Quartz as it directly affects our industry.
Quartz Phantoms for Collectors
The most basic market for quartz is with collectors looking for the rare and unusual when it comes to quartz phantoms. These are generally crystals that were growing but stopped for a while. As the surfaces become coated with various materials in the growth medium, the quartz would start growing again thereby engulfing the original surface inside the crystal as what appears to be a crystal inside a crystal. While it is a rare occurrence that two quartz crystals will be growing within one another, usually these phantoms are formed by the process of intermittent growth. These are in high demand by collectors and an important revenue stream for gem and mineral dealers.
Amethyst Gemstones
When it comes to quartz gemstones, amethyst has to be at the top of our list. With centuries of history dating back to the ancient Greeks who thought that wearing an amethyst would prevent drunkenness (wonder how that worked out for them), amethyst has been a favorite of customers the world over. The finest amethyst come from the Jacobina Mine in Brazil, previously operated by my former employer, Amsterdam Sauer. Amethyst will offer rich purple to violet colors with the finest having red flash effect colors when viewed in full spectrum lighting.
Citrine Gemstones
Citrine offers a variety of light to intense colors in the yellow to orange range. Natural citrine is quite rare. Most of the citrine in the market owes its color to heat treatment of lower quality amethyst. This should not be a problem with selling citrine as most gemstones are heated to some degree to improve color and clarity. Citrine can vary from light yellow to beautiful dark madeira color and is prized by consumers for its earth-based tones of color.
Ametrine Gemstones
One of the rarest forms of gem quality quartz is ametrine, a combination of amethyst and citrine in a single crystal. These are crystals that grew with one coloring element for a while, then the medium in which they were growing changed in chemical makeup. This caused the gem crystal to grow as an amethyst for a period of time, then turn colors to citrine. They are quite rare with the finest coming from the mines of Bolivia. Be aware that there is a myriad of lab created ametrine on the market. Below left is a natural Bolivian ametrine crystal, and right a faceted Bolivian ametrine, both from the ISG Student Reference Collection.
Prasiolite Gemstones
Another of the rare forms of gem quality quartz is prasiolite, the light green variety. Extremely rare in nature, the vast majority of prasiolite on the market is light colored amethyst that is heated to create the light green colors.
The importance of quartz goes far beyond jewelry, however. Most jewelry store staff work with quartz every day in a way they are not aware.
Keeping Time with Quartz
Lab created quartz has been around for decades, owing to the need for perfectly formed quartz crystals for use in electronics. The perfection of which quartz can be grown in a lab eventually led to the ability to create amethyst and other quartz gemstones. That will be for another story. However, anyone who works in the watch department works with quartz crystals every day. Below are two examples of hydrothermally grown quartz crystal on the left, and a plate of quartz that helps make the quartz watches in your watch department to keep accurate time on the right.
Below left is a look inside one of those quartz watches. At right is what the quartz crystal looks like inside the watch, very much like a tuning fork. When you put a small electric current through this crystal it vibrates at a very constant 32,768 times per second, or “hertz”. For every vibration number 32,769, your quartz watch forwards the second hand by one second. Think about it like this, in one hour the quartz crystal in your quartz watch vibrates 117,964,800 times to click off 3,600 seconds per hour. To learn more about the amazing study of watches I invite you to join us for our Introduction to Watches Course here at the ISG.
Gemological Properties
Colors: Violet to purple. The finest quality will show a red flash effect when rotated under an incandescent light source.
Wearability: Very good. But extreme heat should be avoided as the color can bleach out if heat in excess of 800 degrees F (470C) is applied.
Crystal System: US – Hexagonal; World – Trigonal
RI: 1.544 – 1.553
Birefringence: .009
Optic Character: Uniaxial Positive U +
Absorption Spectra: None that will help.
Specific Gravity: 2.63 – 2.66 average
Hardness: 7
Transparency: Transparent
Synthetics: Yes. Very prevalent on the market.
Imitations: Many including purple scapolite.
Color Infused Quartz
Be careful about color infused quartz that is being sold on the market as emerald. Particularly with internet sellers such as eBay and Etsy. Due to the close refractive indices to beryl, the unprepared gemologist may mistake this color treated quartz for emerald. Other lab created amethysts and citrine are ubiquitous on the market requiring highly technical testing equipment to make the distinction from natural gemstone quartz.
We could obviously go on for hours talking about this simple but amazing gemstone material. This is just the basic overview of how quartz impacts jewelry stores everywhere, and on many levels. It is all about revenue streams and operating a successful jewelry operation. Quarts is and always has been an important part of that success.
I hope you enjoyed this fun look of how gemology plays an important part in all phases of a jewelry store operation. If you are interested in the world’s most amazing (and affordable) study of gemology and jewelry appraisal, we invite you to review our program by clicking here.
View this educational page on our website ISG The Story of Quartz.
View additional ISG Education Series articles below:
- The Story of Ammolite
- The Story of Aquamarine
- The Story of Quartz
- The Story of Abalone Shell
- Where Gemology Meets Horology
- The Story of Amber
- Brazil: Where Gemstones Form
Visit the ISG website to learn more about our world-class programs in gemology and jewelry appraisal at our low tuition rates. International School of Gemology.
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