I’m curious how others value Faceted Prasiolite ?
The IGS Gemstone Price Guides have Quartz, Citrine and Amethyst each with varying values but there is no listing for Prasiolite.
I am aware that it can be produced by Heat-Treating or Irradiating Amethyst and it can grow naturally. I have no idea how my Prasiolite came to be but I’m also unsure if it has an affect on the value of this type of Quartz ?
That’s true. Quartz is Quartz but the Amethyst variety of Quartz is valued much higher than your run-of-the-mill, clear Quartz among others. Proof of that is in IGS’s own Price Guides. As mentioned in my original post, IGS has prices for each of 3 different Quartz categories.
I’m just asking which category or table would others use to price their Prasiolite since IGS does not have a specific value for it, unlike they do for other Quartz’s ?
I would really not use the IGS price guides as a reliable indicator of the price of a gemstone. It really doesn’t give specific prices, just ranges. It doesn’t tell you what to discount for inclusions, treatments, color or specific size. Yes, it will tell you that ruby can be worth more than sapphire and sapphire is worth more than tanzanite and tanzanite is worth more than iolite, all other things being equal. It really doesn’t go beyond that. As far as valuing prasiolite in your hand, there are several problems. While there is only one small mine in Brazil that is reportedly producing natural prasiolite at present, there is also heat treated amethyst that turns to prasiolite and then there is synthetic green quartz. I don’t think there is a way to reliably distinguish the natural prasiolite from the heat treated amethyst. There is also no completely reliable way to distinguish either of these from a synthetic without sophisitcated tests available only in big labs. Some synthetic quartz has inclusions that prove synthetic, but not all. Twinning used to indicate natural, but there are now synthetics that are produced from twinned seeds that show twinning, so that no longer distinguishes. There are some natural quartzes which have inclusions that distinguish them from synthetic, but you still don’t know if they are natural prasiolite or heat treated amethyst. So all said and done, probably the best you can do if you are being honest is assume it is a garden variety of quartz if it shows some natural inclusions and you are up on your microscope analysis of natural vs synthetic. I saw some supposedly natural prasiolite on GemRockAuctions tonight for about $6/ct and I would suspect that is a good estimate of price for ring sized stones. I’d value it like good to fine quality amethyst at best. -royjohn