Rough goldstone is usually sold as broken chunks and as slabs suitable for cutting cabochons. The chunks range from small pieces used for rock tumbling to large pieces weighing over 50 pounds. Although goldstone is a man-made material, it varies greatly in quality, appearance, and suitability for use in making cabochons, tumbled stones and other objects. The buyer needs some knowledge of how goldstone is made to make an intelligent purchase.
Goldstone is made in a large heated vessel that might produce 100 pounds of material or more. After it has been heated and held at the proper temperature, the glass is allowed to cool slowly. Slow cooling allows time for the reflective metallic crystals to grow to a large size.
The batch cools fastest near the outside of the vessel. The smallest crystals in the batch are usually found near the wall of the vessel because that is where the rapid cooling occurs. There, the crystals can be too small to produce the desirable glittering effect that gives goldstone its appeal. The crystals usually grow progressively larger towards the center of the vessel, where cooling is slowest.
Within a batch, the glass can have areas with few visible crystals, areas with numerous gas bubbles, and areas of slag. All of these areas are unsuitable for use, and any buyer who is paying by the pound should make sure that the price paid does not include the weight of useless material.
So, if you are buying rough goldstone, pay attention to crystal size, the presence of areas without crystals, the presence of gas bubbles, and areas of slag. Slag, bubbles, and areas lacking flash will be unusable as “goldstone.” Also, some goldstone only exhibits aventurescence from two directions instead of from all directions.
It is best to buy goldstone where you can inspect the rough from all angles in directional light. The next best way is when you can see photos of the piece that you are going to buy from multiple directions with views that are close enough to see the flashing crystals. Buying chunks or lots of goldstone shown in a single photo or sight-unseen from an internet vendor is a risky spend of hard-earned money.
Goldstone Rough: This is a large chunk of goldstone rough that measures about 8 inches across. Some parts of this specimen would be suitable for use in lapidary projects. However, other areas are clearly not as desirable. On the left side, you can see some slag and areas without visible sparkle. This specimen is a good example of how the quality of goldstone can vary greatly even within the same batch