I've written about strange, dodgy, fraudulent or unusual gems being offered on the market as well as manmade, treated and created gems or those made using recycled materials.
This resource now collates all the information so that anyone buying gemstones can easily use it for reference. It will be added to and updated as I find new information or gemstones (if you know of one that isn't here, please let me know so that I can investigate). It would be great to test all gemstones in a laboratory, but using this high-tech equipment is expensive so information is provided from personal testing and research.
While this information is no substitute for gemmological training, I hope it will give you an insight into what you may encounter when shopping for gemstones.
If I can help someone make a more informed purchase, that would be brilliant. Hope you find it useful!