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 (1903) was begun. The squadron returned to the Port of Bahia without success. A further attempt to find "Möwe" was made on 24 January when "Amethyst" was joined by , but this was also unsuccessful. Patrols to search for German surface raiders were also conducted in April and May 1917. After a long stay in Rio de Janeiro, "Amethyst" sailed on 5 April 1918, patrolling down the coast inspecting vessels and arriving in Montevideo on 10 March. On 31 May 1918 "Amethyst" left Bahia, Brazil to return to Devonport. On the way home, she met off the coast of Sierra Leone