We applied fluorescence fingerprint to various rubies, and analyzed the data by principal component analysis. As a result, it was found that three features mainly affect fluorescence fingerprint of ruby. The first is the red fluorescence around at λ_em=694 nm. The second is longer-wavelength fluorescence of Cr clusters around at λ_em=774 nm. The third is direction of optic axis. On the score plots, Myanmar and synthetic ruby stones were separated from the others. Especially fluorescence fingerprint of the Myanmar ruby was characteristically different from the others because of fluorescence of Cr clusters. It is suggested that fluorescence fingerprint of ruby is partially available to geographic origin determination.

Raman spectroscopy is an analytical technique with many advantages such as non-destructive, quick analysis, no sample preparation, and high spatial resolution, and is routinely used by gemological laboratories for the identification of gemstones and their inclusions. This paper reviews the principle of Raman spectroscopy, details of the equipment and examples of its use in gemology.

This paper reviews rare types of diamond growth. It is quite popular that diamond grows from molten metal under high pressure and temperature conditions. The diamond is usually grown at a fixed temperature, but there are only a few reports that show growth morphology of diamond formed while the temperature is decreased. This paper presents growth pattens formed on diamond surfaces when the growth temperature is rapidly decreased, and diamond dendrite formed with temperature decrease at slow rates.