40mm (approximately 1 1/2 inches) goldstone donut. Goldstone is a manmade glass with tiny flecks of copper suspended in it and it has been made and enjoyed for centuries.
These work very nicely with the quality satin necklace cords that I make.
The gemstone donuts I carry are a natural product. Each one will be unique and may not be exactly like the ones pictured. Each stone varies and each shipment I receive has variations in how the item was carved. Some are thicker than others. Some have larger holes than others and some have more rounded edges than others. Each stone has it's own unique characteristics. The color range for some types of gemstones varies quite a bit. I have pictured at least two to show some possible differences.