CHAPTER 17: New Case Studies: Diamonds, Jades, Corundum and Spinel

New and updated applications of Raman spectroscopy in gemmology are described. The manufacturing of synthetic diamonds makes it necessary to study their PL bands more thoroughly than previously, while avoiding contamination from nitrogen or water. Separating synthetic from natural diamonds can be done with the support of a Raman instrument. Several museum pieces described as jadeite are in fact omphacite, or a mixture of jadeite and omphacite. With Raman spectroscopy, these minerals can easily be separated from another in a non-destructive manner. Inclusion identification with Raman spectroscopy, and comparing results with the literature data from other destructive findings, allows one to identify the origin of a gem, helping to separate older sources from newer ones in museum pieces. Zircon inclusions, like the mineral zircon, become metamict over millions of years due to radioactive elements in its structure. Metamictisation broadens the Raman peaks, which can be reversed by heating. The peak width of a zircon inclusion of known origin can be directly related to its heating state. Red spinel from Burma often has a brownish overtone that can be removed through heat. When comparing Raman or PL spectra of heated with unheated spinel, a broadening of the major peaks is observed.