The History of Quartz Treatment


Recently there have been questions about a treated quartz with a light yellow/green color similar to chrysoberyl. The material is traded in Brazil under the name Ouro Verde. I am actually the one who developed the process. In this process, the gem is not nuked, which implies nuclear irradiation. It is irradiated with cobalt 60 (gamma) at a very low dosage, which dissipates as soon as it goes in. Next, the gem is heated in a household toaster oven in several steps. The location of the mine along with the exact formula for this material and numerous other treated quartz is included below.

So, you know why it took so long for our industry to discover quartz treatments other than smoky? It is funny. You must understand that the art of gemstone treatment by irradiation is very new. It has only been around for 25 to 30 years at the most. The first topaz treatment was a simple procedure with cobalt 60 that produced, in the right materials, only a very light blue stone. This is same process that occurs in nature. Diamonds had been successfully irradiated at this point, but primitively. Blue topaz is what really started the ball rolling, mainly due to the fact that the profit incentive was there.

Prior to that, natural light blue topaz was rare and fetched $300 a carat in Brazil. The white material was abundant and considered almost worthless. You could buy ton lots of giant white topaz from the Marambia mine, the best quartz for treating, for $5 to $10 a kilo. Sizes ranged up to 20-30 kilos and the stones were flawless. Today you would have a hard time to find 10-20 kilograms per month. The sizes are smaller and prices are $400 per kilo and up.

With this type of incentive the natural progression was to invest in R&D. It did not take long for the discoveries that showed bleaching prior to treatment, different dose rates, and different types of irradiation gave improved results. So today we have an assortment of colors that you would never encounter in the wild, including iridescent greens and super blues.

Now, here is the rub. As the topaz comes out of the irradiation treatment it is an opaque black. There is a subsequent, low level heat treatment between 350 to 500 degrees F that takes one to two hours. At the end, you have all blue stones with the exception of a few pieces that stay opaque black. These were quartz and many folks would trash them.

Myself, I used to sell them by the pound for use as black onyx. They exceptionally good for this purpose, as the black went all the way through the stone. Black onyx, you must know, is created by soaking a gray agate in honey or sugar, then placing it in heated acid to burn the color black. This acid process only penetrates a few millimeters. If you have a project involving slicing the rough in half, or grinding deep, you go into the original color of the material and you lose the black. Commercial black onyx, manufactured mainly in Germany and sold in slabs, got at best $100-200 a kilo. This has not changed for a century. The preferred gray agate, originating out of Rio Grande do Sul, Brazil, still blankets the ground in that area. It is sold for only a little over the freight costs.

So there it was, I have black quartz that only brings $100-200 a kilo and the irradiation costs could get up to $1,000 a kilo at the time. Taking them to the next higher heating temperature involved a closed crucible, as to go above 500 degrees F you need a casing oven. Trying to salvage an apparent loss, I tried various heating combinations, but they all involved higher temperatures which needed closed door equipment. Prior to that I had used a toaster oven that has a glass door so you can watch the results and know when to stop. The best I achieved with a casting oven was smoky quartz. Usually the result was to revert them to clear white quartz which had a lower value, though the smoky quartz was not much better.

Over time I learned that it only requires .5 to 1 megarad of cobalt 60, or the like, to create it and pretty much all quartz will turn color. The value of the treated quartz was $5 to $10 a kilo, so again I actually increased my loss with the extra work and electric bill.

As the blue topaz market waned, I gravitated toward experiments in irradiating white beryl. I discovered there were considerable differences in the effects, depending on the temperatures of the subsequent heating. At this point I was living in Minas Gerias, Brazil, with a 15-man factory set up to cob the beryl flawless at the source. My hopes were that irradiated beryl would become the next Blue Topaz rage, but with beryl you have several defeating problems.

The availability of white beryl is sporadic — your results vary within a given mine and even within a given stone. One also needs continuous commercial feasible quantities, uniformity, and, most importantly, to know the amount of dosage needed and what the effects will be on the majority of the beryl you treat. To achieve top colors with beryl, most pieces need dosages of 5,000 megarads and a high dosage rate, (MEV – how fast the irradiation penetrates the work piece). This is best achieved on a linear accelerator with electron irradiation. This is not only prohibitively costly, but because most beryl can have a reactive content of cesium, you might be left with a product that needs 100 years to cool. You could achieve the same effects, less the drawback of the residual irradiation for long periods, by repeated dosage, over one to two years, as irradiation is cumulative.

It was pretty tough to overcome these obstacles to produce a mass commercial fad. And curiously, there they were again, those stubborn black quartz mixed in with my beryl; however, this time I was lucky enough to observe Brazilian lapidaries heating aquamarines and tourmalines with just a glass test tube over a Bunsen burner. This art has been practiced for centuries. I had never considered it as it was primitive and because you could only fit so many stones into a little test tube. You could never supply the world a product line this way, but at least I could see through the glass and get an idea of what would happen to the beryls from different mines.

It worked! Next was to determine the exact dosage, for the exact mine or even the type of beryl at a location, and the proper heating temperature. This appeared to be a life’s work and I am still at it; however, here was my opportunity to see exactly the progression of the irradiated quartz on heating as well. I had observed in the past, what I considered to be the usual progression of color when you heated amethyst to make citrine by accident. Apparently if  you were to open the oven door in the middle of the process, you might think you overheated them to white. The amethyst first goes to clear, then into citrine. So I wondered if the irradiated black quartz was passing through a middle color. My good luck, as all clear quartz does not take on other colors when irradiated, which further complicated and delayed this discovery.

The first pieces I heated in a test tube went to a glowing canary yellow, almost electric. Excited I heated a couple kilos of irradiated quartz of unknown origin, that I had kept from the blue topaz days. Unfortunately, I had picked up these quartz during my travels and they  came from locations scattered all over the world. As a result, and much to my delight, I got almost every color of the rainbow. I got lime greens, tourmaline greens, every shade of orange, and even red.

In the following year, as more of the world’s quartz locations are tested, we were in for some pretty fantastic new varieties of the gemstone quartz. Just as important, quartz is found in abundance and I have observed very little deviation in color from any given location It is still inexpensive and the amounts of dosage needed are low and in a general range. In other words, we had all the ingredients for a commercial success! To that end I have secured the Ouro Verde mine. Interested parties may inquire for any reason. Experimenters and mine owners, I am happy to share my research.

Mark Liccini
Gemstone Rough Dealers since 1970

About the author
Mark Liccini
The late Mark Liccini began his career as a stone carver in the 1970s and worked for many decades as a renowned lapidary. Mark mastered the art of gemology, gaining degrees from Gemmological Association of Great Briton,and Columbia School of Gemmology, Wash.D.C.
All articles by this author