Crystalline Quartz Buying Guide
Ancient civilizations thought the gods had petrified ice to make quartz crystals. Although our understanding of mineralogy has greatly increased, some still believe this gem holds mystical qualities. Indeed, with so many varieties, quartz offers something for all types of gem collectors. Available in extremely large sizes and often cut with mesmerizing designs, quartz is an excellent choice of material for lapidaries just learning their craft. In addition, its low cost makes it perfect for buyers on a budget and those looking to keep up with jewelry trends without breaking the bank.
Crystalline Quartz Buying and the Four Cs
The IGS quartz value listing has price guidelines for smoky quartz, rose quartz, rutilated and tourmalinated quartz, quartz with lepidocrocite, and star quartz. Separate value listings for amethyst, citrine, and gold in quartz contain price guidelines for these varieties.
Quartz is a large family of gemstones. Not surprisingly, it occurs in many colors and varieties.
Without trace impurities, quartz is colorless. This abundant material occurs in very large sizes. Often called “rock crystal,” colorless quartz can serve as an inexpensive alternative to other colorless gemstones.
Doubly terminated rough crystals are somewhat rare. Gem enthusiasts sometimes erroneously call these gems “Herkimer diamonds.” This misnomer comes from their source, Herkimer, NY, where they occur in abundance. With high transparency, these gems sparkle when rough.
Ranging in color from light tan to nearly black, smoky quartz can simulate imperial topaz. When faceted and set, these gems can make lovely jewelry pieces with their deep chocolate to opaque black tones. Although inexpensive and abundant, even in large sizes, you’ll rarely see smoky quartz used in jewelry. Thus, you could choose these gems for a unique custom jewelry piece.
Rarer than other varieties, the delicate pink hues of rose quartz may be difficult to find with transparent clarity. The pink hues of rose quartz arise from fibrous inclusions of a mineral similar to dumortierite.
Some specimens exhibit the Tyndall scattering effect. Fine particles within the gem scatter light, giving the stone a blue hue.
Extremely rare pink quartz can be transparent, but specimens over 20 or 30 carats are rare. This material can be synthesized by growing quartz with aluminum and phosphate and exposing it to gamma radiation. Although the color may fade in sunlight, irradiation can restore this color.
From light lavender to deep purple, amethyst is the most popular form of crystalline quartz. These gems are often somewhat cloudy. Hence, high transparency and deep color characterize the most valuable specimens. For more information on this February birthstone, read the IGS amethyst buying guide.
Rare specimens may exhibit multiple color zones. A very rare combination of amethyst and citrine, ametrine occurs due to slight changes in temperature during its formation. While their colors don’t reach the highest levels of saturation, these gems are still valuable.
Green quartz, or prasiolite, forms when certain amethysts are heated. Natural specimens are extremely rare, but treated stones are available.
Blue quartz, or dumortierite quartz, derives its color from inclusions. This opaque to translucent stone is largely a collector’s mineral.
Due to its abundance, quartz specimens with visible inclusions hold no value. However, some spectacular exceptions do occur.
As an inclusion in a clear quartz crystal, rutile, or titanium dioxide, can be stunning. Visible as golden, needle-like inclusions, they can cluster in parallel lines or intersecting patterns. Well-fashioned cabochons of rutilated quartz have become quite popular for their unique look. Faceted gems can also sparkle while exhibiting these golden inclusions.
Gold in Quartz
Gold inclusions in white milky quartz can make lovely features in cabochons. Jewelry with a light sparkle of gold from these unusual gems can be a unique novelty.
Clear, colorless quartz cabochons sometimes feature black, needle-like tourmaline inclusions. As rough specimens, generally, tourmalinated quartz with color will sell for a premium.
Quartz with Lepidocrocite
An iron oxide mineral, lepidocrocite can create spectacular patterns in clear, colorless quartz. Due to its red color, this variety is sometimes called “fire quartz.”
You can find gem-quality quartz in any cut. Because of its abundance, a poorly cut quartz doesn’t hold value. However, very well-cut gems are also rare, due to the material’s low intrinsic value. Still, there are spectacular fantasy cuts of quartz specimens. For specimens with these unique cuts, their value derives largely from the quality of the cut.
As for cabochons, a star quartz should exhibit a bright, sharp star. Other included specimens should have well-featured inclusions.
One of Earth’s most abundant minerals, quartz is available in all sizes. Thus, for most varieties, the price per carat doesn’t increase. Still, large stones of exceptionally high quality can be difficult to find. Pink quartz is generally unavailable in sizes above about 20 carats.
Quartz has a hardness of 7 on the Mohs scale, making it fairly resistant to scratching. However, because specimens with inclusions may be prone to fracture, avoid impacts. Overall, quartz makes an excellent jewelry stone, especially for pieces prone to wear and tear, such as rings and bracelets. In addition, its large sizes are ideal for statement jewelry.
Quartz color can be altered by irradiation and heat treatments. For example, green quartz, or prasiolite, is almost always the product of such treatment. Furthermore, heat treatments can lighten amethysts and even turn them into citrines. (Since amethyst has greater value than citrine, this would be an unlikely and unprofitable decision).
Synthetic quartz is available, and synthetic amethyst isn’t uncommon. These make inexpensive alternatives to natural quartz. However, with the low cost of natural material, small synthetic gems are uncommon. As always, be wary of any deal that seems too good to be true.