Blue Topaz or Aquamarine?

Once I got back down to the bottom of the mountain (hill), I went back to the faceted gemstone seller and asked for a piece of Blue Topaz rough (I will call it this, in deference to her :). She sold me a light blue-green stone for five dollars.

I took it back to Phnom Penh with me and did some digging in my books. Along the right had side of this post are some views of this piece of crystal. I don't have the ability to measure its specific gravity or reflective index (that would put to rest the question easily), but I can list some arguments in favor and against it being Aquamarine based on what I learned or could see.

1) Aquamarine is not ruled out by its color, nor is Topaz. Both stones occur naturally in low saturated blue-green colored gems. On color it could be either.

2) Topaz and Aquamarine are known to occur in the same geologic setting, so there would be nothing surprising about Aquamarine being found in a location where mostly Topaz had been found until now. In fact Aquamarine is often found with Rock Crystal and with Smoky Quartz as Topaz is here. Nothing to rule out Aquamarine here.

3) The gem sellers all say that this light blue stone is more difficult to cut than is Quartz (there never was a question of whether this was quartz, quartz does not occur naturally in blue). They could not say if faceting the stone was more difficult or easier than for Topaz. The ones who believe that this stone is naturally occuring blue Topaz say that cutting is the same as cutting Topaz itself. If it were Aquamarine, it would be harder than Quartz, but possibly as hard as Topaz. Nothing determinative here. Easy to see why the cutters cannot tell. (Mohs is a 10-point scale and a standard gemological standard for measuring relative hardness. Diamond is 10.0.)

Quartz (Mohs=7.0); Aquamarine (7.5-8.0); Topaz (8.0)

4) To my mostly untrained eye, the crystal form of the stone appears to be hexagonal. If I am right, that might in and of itself rule out the orthorhombic Topaz.

5) The piece of crystal rough that I bought has striations parrallel to the long axis of the crystal. Both Aquamarine and Topaz are known to display that, though most of the Topaz crystal rough I saw at this site (and bought on a previous visit)  had been worn and pitted by their travel to a final alluvial deposit. On the other hand, and contradictorily, a lot of the quartz was so finely formed and unmarked that the gemstone dealers talked about how it looked as if it had been hand cut and polished!

So, until I can get the specific gravity of this stone measured (Aquamarine: 2.63 - 2.91, Topaz: 3.5 - 3.6, strangely different sources vary in the numbers they provide), or measure the refractive index on a cut stone, I may be out of moves.

Unless. Unless I go back and look at two cut stones, one clear and clearly Topaz, and the other light blue, same cut, same carat weight, and see if the Topaz is smaller (higher specific gravity).

Or. Or, ask for two stones that look to be the same physical size (volume) and see if the blue one has a lower carat weight.

Yeah. Yeah, I think that is what I will do. And if it appears to be Aquamarine, I will buy me a couple of stones. You should see the international retail prices for good color stones. :)

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At the Base of the Mountain

A sandy, one-lane road leads from the national highway to the base of the mountain where faceted topaz is sold. A military-style checkpoint monitors a drop gate over this road a kilometer short of the mountain, but checking through there is quick, a simple formality, and nothing in the pleasant interchange reveals the purpose of the facility!

Cars can easily make the five-kilometer drive in, if the weather is dry, and motorbikes have very little problem except for the parts of the road where the white sand is at its thickest, back wheels can slough and spin, but if you are using a local driver, no worries. They are experts.

A dozen women have set up shop at the base of the mountain, there is plenty of parking and shade. Their display cases are glass and metal, but their 'stores' are bamboo, slim-cut timber with sugar palm foilage on the roofs. What you would see anywhere in rural Cambodia.

All of the stones are very clear, with limited inclusions, many are colorless, some with a hint of yellow (see the stones at the head of this blog). As you would expect with 'raw', untreated (but faceted), natural Topaz -- the stones are brilliant (in the past they have been mistaken for diamonds, see for example, the Portugese 'Braganza Diamond').

One should be aware of that the displays present topaz and quartz both of which come from the site. The smoky topaz and the smoky quartz may be difficult to differentiate, except that topaz 'feels' heavier (compare stones with similar volumes, the carat weights should differ), its specific gravity is 33% greater than that of quartz (approximately 3.5 versus 2.6). To me, topaz also has a kind soapy feel, quartz a glassy look and feel (but that is very unscientific).

If you are unsure of your own differentiations, you need not worry, I believe that these dealers are honest, They know the price they will all pay if word of mouth indicates that they are cheating customers. They are fully aware that the hardness of Topaz is greater than that of quartz, for them differentiation is easy, as they sub-contract the cutting. If the lady says that it is Topaz, you can take it to the bank.

There is a very wide range of cut stone sizes, with some very large ones available. But it in this case size is not necessarily better, hard to know what to do with a 50-carat cut topaz! And with prices between $5 and $10 per carat, total costs can mount quickly. And if you are used to cut citrine or amethyst, a five-carat topaz will seem somewhat small -- again its density is greater than quartz.

The lady in the picture above was the first one to show me what they all call blue topaz. The color of all the stones that I saw was blue-green, a sea-green, as the Khmer has it (poa duk samot - seawater color). The saturation of the color varies from stone to stone, but the most deeply colored are still very light.

When I was told that the stone was a natural blue topaz, my initial reaction was disbelief, disbelief out of my own ignorance. On returning to Phnom Penh I turned to the trusted Handbook of Gem Identification (Liddicoat, GIA), and yes, there are naturally occuring Topaz gemstones that are blue, but their commercial value is low since much more saturated colors are easily available from heat-treated and irradiated natural stones.

Back at the bottom of the mountain, another lady sitting with the seller I was speaking to, bashfully whispered 'aquamarine', which I did not know what to make of, since I knew little about the stone.

I aimed to learn more. Aquamarine would be interesting. If Topaz is more valuable than Quartz, though both are very common, good faceted Aquamarine is significantly more valuable than Topaz.

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