Written by Modern Jeweler On May 2, 2013.
Editor’s note: Andesine feldspar is currently the subject of several lawsuits. For more updated information on this gem, check our Gem Profile on Oregon sunstone. The following is the original text from our March 2006 Gem Profile, which was written when the attractive and mysterious material was first appearing on the market.)
ANDESINE: Red-Hot Feldspar
You’ve got to hand it to Jewelry Television, the 24/7 gemstone shopping network based in Knoxville, Tennessee, that has positioned itself as a gemological Discovery Channel. The station knows good things when it sees them. And when, as is often the case, it’s the first to lay eyes on an affordable new gem, it lays enough cash on the table to make sure no one else will see it until it has built a thriving market. With a viewer base of 65 million people, the network often needs months to satisfy large audience appetites.
Nevertheless, Jewelry Television doesn’t blindly lunge into new stones. Because it takes so many risks, it must temper need with caution, giving each newcomer several screen tests to see if it will merit voracious stocking. Of all the gems the network has premiered, none has risen to quicker popularity than andesine, a red plagioclase feldspar whose origins remain a closely guarded-or deliberately muddled-secret. At first rumored but never confirmed to be from the Congo, the current source is most likely western China, possibly neighboring Mongolia or Tibet.
From a marketing standpoint, andesine has all the traits of a Chinese-origin or Chinese-controlled gem. That usually translates into a sell-now, sell-all-you-can philosophy. Since Tucson 2004, supplies of red (as well as green) feldspar have been near ceaseless, something which has worked to Jewelry Television’s advantage ever since it first took a chance on the gem when introduced to it at the show.
Chinese dealers priced their andesine to move from the start. But once this feldspar proved a winner, Jewelry Television bought it in price-pummeling bulk. Last month at Tucson 2006, the network purchased tens of thousands of carats just from two suppliers-and put in open-ended orders for future production when and if it materializes. “Demand is staying way ahead of supply on this one,” says buyer Jay Boyle.
No wonder the station charges $80 to $200 per carat-depending on color, clarity, and size-for the four hues of andesine it offers: red, orange-red, orange, and honey-red. While some exceptional stones fetch more, even their several hundred dollar-per-carat prices reflect the network’s immense checkbook leverage. What makes andesine so telegenic? At its best, this gem boasts a rich red that invites show hosts to compare it to ruby. Is this an exaggeration? “With a below-average return rate for andesine, shoppers are obviously happy with what they receive,” says gem buyer Shawn O”Sullivan.
Incredibly, more than 90 percent of the andesine Jewelry Television sells is loose, which suggests that most buyers are collectors-or, perhaps, still pondering ultimate use. Since network customers tend to be versed in the gems they buy, they probably know andesine has a hardness of 6 to 6-1/2, which should deter mounting in rings. But so does tanzanite and that’s been finger fare for nearly two decades.
As andesine’s red glare spreads off screen to jewelry stores, the gem is coming under intensive gemological scrutiny. Like garnet, feldspar is a large, sprawling family and classification has been tricky, if not controversial. So before putting the stone on air, Jewelry Television asked GIA for nomenclature guidance which it is now following-until or unless the institute changes its thinking.
Before andesine appeared, the best red feldspar available was medium-toned, orangey material from Oregon known as sunstone because of its shimmering reflections called aventurescence (schiller) from tiny crystals clustered inside. Sunstone, which is a market rather than a mineralogical name, belongs to the oligoclase branch of the feldspar family-a family that needs genealogy charts to figure out precise memberships in it.
Apparently, andesine is an intermediate member between oligoclase and labradorite, just on the borderline with the latter. Such overlapping chemistry tempts merger names such as “andorite” and “labrasine.”
Overall, family placement in the six member (albite, oligoclase, andesine, labradorite, bytownite, and anorthite) plagioclase group depends on several factors, including refractive index (around 1.55) and shifting ratios of albite to anorthite (the flanking members of this group).
One thing for sure, andesine is not sunstone because it lacks schiller and is usually far deeper in color. However, we’re not too excited about calling it red labradorite either. To us, that’s like calling pink or even golden sapphire by the name of ruby, especially since only a small percentage of andesine is real red in the sense that sapphire is true blue. What’s more, andesine also occurs in green that exhibits other colors such as red in alexandrite-fashion under different lighting conditions.
Here we come to one of the most curious elements in the andesine success story. Red andesine is the first feldspar I can think of that is appreciated for pure monochromatic color the way, say, spinel is.
It is green andesine that is more characteristic of feldspar because it lives up to traditional expectations of color play and other special effects for this gem group. Remember that moonstone and rainbow labradorite are among the most famous feldspars-and both are celebrated primarily for their blend of color and appearance. On the other hand, red andesine finally puts feldspar in a color class with red corundum to which its very likable best stones are justly likened.