Mineralogical and Macro/micro-Structural Properties of Non-nacreous Pearl from Tridacna gigas (Philippines): a Study on World’s Largest Pearls.

English Abstract:

Recent developments in the field of gemology are now relying more on advanced instruments to understand better the physicochemical properties of pearls. These techniques are used in determining the purity and authenticity of pearls. However, there are very few studies done on authenticating large non-nacreous pearls. The pearl of Lao Tzu (~6 kg), considered as the world’s largest pearl, is one example of a non-nacreous pearl that forms from biomineralization in giant clams. Recently, a large material which exhibits pearl like properties was discovered near the location where the Pearl of Lao Tzu was found. This object weighs ~9 kg. Mineralogical analysis, scanning electron microscopy, infrared spectroscopy, and macro structural analysis were used to figure out the properties of this material, and delineate whether this object was a real pearl. Based on XRD and IR profiles, the material consists of the mineral aragonite. It also exhibits thin laminations which are characteristic of natural pearls. The macroscopic structures present in the specimen like concentric banding, and flame structure indicate the development of aragonite blades common in Tridacna gigas. Based on the initial findings of this study, this object matches clearly the properties of large non-nacreous pearls.