I agree to the discussion. I always test first doubling with my loupe or microscope. Almost always it is easy to find doubling for (high) zircon like red or white ones. If you find doubling - it cannot be CZ. I also test with presidium digital refractometer and Gem-n-eye in parallel. I have good experience with this procedure. But the problem which came up in the last years is India and fake certificates. I cannot understand why Ebay does not take action. If you search for certain stones you get hundreds of offers from India with fake certificates and only a couple of serious offers between. Some are easy to detect like blue rhodochrosite (!), 10 ct “natural” tanzanites for 10 – 20 USD, 4 … 10 ct “natural clean” Alexandrite for 20 USD, and recently 6 … 10 ct VVS “natural” tsavorite “from Kenia” for 10 … 20 USD or “natural” 12 ct bixbite “from Utah” for a couple of USD. Such prices are impossible because so big stones would cost hundreds or many thousands USD. Same with trapiche stones. You find trapiche emerald in the size of 2 …5 ct (and more) for a couple of dollars. In some picture you can already see that this are fakes (despite a certificate from GGL or CGL) because some have 7 sections, other are glued together in wrong direction but you find also some where you are not sure – only the size and the price tells you that it is impossible. My conclusion: be extremely careful with dealers from India. Although some serious dealers exists – most dealers have either absolutely no knowledge and sell what they have been told from dishonest partners or they are dishonest itself. Always compare size, cost, color and shape of rough crystals with other offers in the internet. Furthermore, inform yourself about size and other properties in the articles from IGS or MINDAT database.
