Tuesday, January 11, 2011
Stars in Your Eyes?
Perhaps I am old fashioned but I prefer a Star Ruby or Star Sapphire cabochon over any faceted gem I have ever seen. Old fashioned in the sense that faceted stones are a relatively new style of cutting compared to cabochons that have been the style for thousands of years. The cutting style, however, is not the key to my admiration as the true beauty of the star gem is indeed the phenomenon of light called asterism. A six ray star that glides all around the surface of the dome as one tilts it in the sun. Pure natural magic to my eye.
The more perfect is the star, the more mesmerizing is the effect. Several factors will determine the look.
The play of light is caused by the hexagonal shape of the crystal structure often made of silk-like Rutile inclusions found in corundum. The exception to Rutile silk is Hematite platelets seen in black sapphires from the Thailand/Cambodian border. If the stone is too clear the silk or the platelets will not be enough to make a star so we need the inclusions. When we are fortunate enough to have both Rutile silk and Hematite platelets we will have a double six ray that is naturally aligned to show a 12 ray star with alternating colors in the rays. The Rutile will often show white or light blue rays while the Hematite will often show yellow or even orange rays.
The star will be centered only when the gem cutter correctly orients the axis perfectly so that it is perpendicular to the face. Many stars are thus off center but this is of little concern as long as it is fairly close so one does not have to search hard to find it.
It is best when we can see all six rays. Often an inclusion will block the view of one ray or hair line fractures will distort the star to some extent. Many times the dome of the cab will be flatter than ideal and cause the star to become broader and less than sharp.
The exact dome combined with the necessary clarity and the axis oriented correctly will allow us to see a sharp star with the rays reaching all the way to bottom of the stone.
As in all colored gems, it is the color that dictates the price when all other factors are equal. The color highest in demand for a star is, without a doubt, red. Red corundum is better known as Ruby and a star Ruby of fine character is truly an exciting and rare gem that will command the highest price of all stars. The stronger the red, the better, however, often pink and purple will be secondary colors. Mogok Burma is the very top of origins that such red Star Ruby gems have been found.
The next most favorite color in the world for a star will certainly be blue. There is a great deal more blue than red star Corundum in the world and this we call Blue Star Sapphire. The finest blues come from two places, Sri Lanka and Mogok Burma. Sri Lanka is famous for its Ceylon blue while both locations have produced what is referred to as 'cornflower blue', the top blue in Corundum.
The most common colors found in natural star Sapphires are black and gray. It is far easier to find a fine quality stone in these two colors than any other. A few star gems are naturally purple, pink, green, yellow, orange, brown or white as well as a mix of shades and tones. Often the purples and pinks are also called Ruby like the red with Purple Ruby being called a masculine ruby and a Pink Ruby being referred to as a feminine Ruby. Usually these two colors are called Sapphires in America.
Today many star Ruby and Sapphire are heated to clear some excess inclusions which can sharpen the star. Borax flux is usually added to the recipe in order to heal some cracks. Too high of heat will eliminate the star and this practice is common when the dealer has a higher demand for faceted gems than he does for stars. Often a star needs no heat and is thus left completely untreated. On the other hand we have repaired stars that have been heated with leaded glass, a less desirable product, however still very beautiful in the short run. I wrote earlier in this blog about the leaded glass treatment done to stars, please refer to it for more tips and information of treatments.
A star can be lab created even in a natural stone. It is diffused into the surface of the polished cabochon and could be polished off in a re-cut. These diffused stars are usually easy to spot as they show in most any light and usually have wavy or crooked rays. These lab created stars are also seen in synthetic corundum, the most famous being called a Linde Star, a trademarked name. Production of these synthetics was stopped by the Union Carbide Company in the 70's when the Asians made so many synthetic sapphires with diffused stars available so cheaply that it was no longer worth it to make them with American labor. Today they are still produced in Asian countries as the demand for low cost Star Sapphire and Star Ruby is still strong. Medium grade Star Sapphires and Star Rubies are in constant demand as they are very affordable and have so much flashy character for the money.
Star Sapphires and Star Rubies of all grades have enjoyed a surge in demand as they are often more intriguing to look at than the more common gemstones. I could not begin to count the number of request I have had over the years for blue star Sapphires.
The demand for high grade natural star gems is even stronger these days than it was in the past as these rare gems have become even more rare as supplies have dwindled. My wife is a huge fan of Star Ruby thus I am always on the lookout for prized red star corundum. I acquired a stunning example recently, mounted in a gold ring, and was so impressed with it that I wanted confirmation from a laboratory that it was genuine and not diffused. I took it to AGIS laboratory in Bangkok, an organization that is famous for being reliable and is better priced than the most famous, GIA. Normally on a visit to a lab one only gets to talk with an office clerk that sits behind a security window, however, when I went in to pick up my report on this particular Star Ruby a gemologist came out of the back to shake my hand and talk to me. He was excited about the stone and proceeded to explain to me that three gemologist had studied it and they all concluded that this was a natural star with no evidence of treatment found. In his words, this was "the nice one". I decided to put this one away for awhile.
Stars will always hold a special place in my heart whether they are in gemstones or in the night sky. Fond memories of coming home from work late at night then laying on the mowed grass of my Ohio home with my young sons at my sides all gazing up at the bright star-filled black sky, dreaming together and being ever so thankful for natures wonders and the love of family. Somehow stars and their brilliance seem to hold this magical feeling that gives us hopes and visions of a bright and shining future. Wear yours in good health!