There's a rather interesting film I watched called 'Nothing Lasts Forever (2022)', which talks about the two types of manufactured diamonds - high pressure high

There's a rather interesting film I watched called 'Nothing Lasts Forever (2022)', which talks about the two types of manufactured diamonds - high pressure high temperature and CVD diamonds - https://www.imdb.com/title/tt16317380/ https://www.imdb.com/title/tt16317380/. It talks a bit about natural and manufactured diamonds being mixed together. It sounds like it's pretty difficult to tell the difference between natural and HPHT manufactured diamond, without spectrometers etc. I found this re. CVD diamonds though "You can identify CVD diamonds fairly simply. They have a unique strain pattern that doesn’t resemble that of natural diamonds and strong red fluorescence. In addition, they lack the typical "Cape Line" at 415 nm on their absorption spectrum. Instead, they present a strong line at 737 nm." - https://www.gemsociety.org/article/identification-of-synthetic-diamonds/ https://www.gemsociety.org/article/identification-of-synthet... I think https://www.youtube.com/watch?v=NdsMIG04vHA https://www.youtube.com/watch?v=NdsMIG04vHA (a short clip from Bang Goes the Theory) shows CVD, using acetylene. And they verify with a raman spectrometer.