Due to the number of loions where stones are available, the high value of gemstones and their limited availability, they are often subject to very high US duty rates and stringent import regulations. If you are looking to import gemstones into the United States, this guide is for you. Where to buy: Diamonds. 90% of the import market is tied to diamonds. They originate .
· Stones should be free from calcium carbonate, oxides of iron, and minerals having different coefficients of thermal expansion. Igneous rock show marked disintegration principally because of quartz which disintegrates into small particles at a temperature of about 575°C. Limestone, however, can withstand a little higher temperature; up to 800°C after which .