Amethyst and it can not be differentiated with absolute certainty without advanced gemmological testing (which is often cost-prohibitive). There is one test based on "Brazil law twinning" (a form of quartz twinning where right and left hand quartz structures are combined in a single crystal) which can be used to identify synthetic amethyst rather easily. It is possible to synthesize twinned amethyst, but this type is not available in large quantities in the market. Single-crystal quartz is very desirable in the industry, particularly for keeping the regular vibrations necessary for quartz movements in watches and clocks, which is where a lot
HMS Amethyst (1799) the Île de France some nine weeks earlier and was sailing for Bordeaux with a cargo of cotton, coffee, tea, sugar, indigo, and the like. Still in company with "Nymphe", "Amethyst" captured "Julius Pringle" and recaptured "Active" (4 March) and "Amity" (21 March). Then on 31 March, "Amethyst", with "Nymphe", captured the French privateer "Mars". "Mars" was armed with twenty 12-pounder guns and two 36-pounder obusiers, and carried a crew of 180 men. Cooke described her as being "one of the finest Privateers fitted out of Bourdeaux." The British took "Mars" into service as . "Amethyst" also captured a valuable