GemSelect Newsletter - June 2010
In our newsletter this month:
The Joy of Cabochons Back to Top
A cabochon is a stone that is cut with a highly polished rounded top with no facets, and a flat or slightly domed base. Before the art of faceting was developed, most gemstones were fashioned into cabochons, though some were intricately carved as well. The cabochon is the most traditional of all gemstone forms.
When the horizontal cutting wheel was invented in the late 15th century, it became possible for the first time to create gemstones with complex faceting designs. The fascination with geometry and reflected light during the Renaissance accelerated the development of a sophisticated lapidary art. Yet, even once the technology and skill was available to facet gemstones, cabochons were still produced. They continue to be very popular today. What is the reason for the enduring popularity of this simple design?
In some cases, gems are cut as cabs because they have special properties that are displayed only in the cabochon form. Examples are gems that display asterism (the star effect), chatoyancy (the cat's eye effect), iridescence (e.g. opal) or adularescence (e.g. moonstone).
Most gems that are opaque rather than transparent are cut as cabochons rather than faceted. Lower grade translucent material in gemstone varieties such as sapphire and ruby are also cut as cabs. If the gem material has good color but is not sufficiently transparent or clean to be faceted, it can still be shaped and polished into a very attractive cabochon. It is also common to cut softer stones as cabs, since minute scratches show much less on a cabochon than on a faceted stone.
Aside from these practical considerations, a cabochon exemplifies two of the properties that we treasure in colored gems. The first is that cabochons are pure color. While most cabs have an attractive luster, they don't obscure color with brilliance. Secondly, cabochons are as close to the natural material as you will find in a gemstone. They have only been shaped and polished in a simple way. When you see a large carnelian or lapis lazuli set in jewelry, you are looking at a gemstone that could have been worn by one of our ancestors two thousand years ago.
We stock cabochons in more than 80 different varieties, in almost every possible color. They range in size from half carat opal and chrysoberyl cat's eye gems to star rose quartz stones weighing over 600 carats. A number of varieties are quite rare, such as ammolite, hemimorphite, smithsonite and sugilite. In total, we have over 5,000 cabochons in our inventory.
Rare and Unusual Gems Back to Top
Each month we feature a rare and unusual gem from our inventory. This month we feature a rare 550 carat rutile quartz from India:
Huge Rutile Quartz from India
Rutile (or rutilated) quartz is clear or smoky quartz with inclusions of rutile. Rutile is the mineral name for natural crystals of titanium dioxide. The rutile needles form lovely patterns like miniature sculptures. Every stone is quite unique - some have delicate hair-like intersecting needles; others have dense clusters of thicker needles. Very large transparent stones that are free of defects are rare, so this huge but quite perfect rutile quartz from India counts as a true collector's item.
Customer Questions Back to Top
Every month we answer questions of general interest from our customers. Please feel free to send your questions or suggestions to our support team at firstname.lastname@example.org!
When I place an order on your website, how do I enter a shipping address which is different from my billing address? JG, USA.
With our new payment system, if you make your purchase with a credit card, you'll first be asked to enter your billing address for the card. Then you have the option of providing a different shipping address for your order. You can also enter any special requests on this page.
If you use PayPal for payment, you can add a note to your payment on the PayPal site to request that we use a different shipping address.
I've seen some quantum cut gems on offer recently. Do you have some information on this cut? Thank you. BL, UK.
"Quantum cut" is a marketing term for what is known in the gem trade as concave cutting. This is a fairly recent innovation, dating back to about 1990, that involves cutting a gem with facets that are curved or 3 dimensional, rather than the traditional flat, 2 dimensional facets. The result is that more of of the ambient light is refracted as brilliance. Generally only the pavilion facets are concave cut, with flat facets on the crown. This often creates unusual reflective patterns, especially when the gem is viewed face-up.
Concave cutting works best with light-colored stones and can make dark stones look even darker. Since concave cutting involves a greater loss of raw material, it is most often reserved for less valuable gems such as quartz, fluorite and topaz. Click the link to view samples of concave cut gems.
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