Green Amethyst: Value, Cost, and Adornments Data The cost of green amethyst shifts broadly relying upon the quality and size of the gemstone. The gemstones which are more modest in size and are of lower quality can be moderately reasonable which makes them open to a wide scope of buyers. In the interim, stones with bigger sizes and top quality can be very costly and are for the most part valued by authorities and specialists. Different factors, for example, the presence of defects, the power of the green tone and the unpredictability of the slice all add to the pricing of green amethyst jewelry.