Study On Gemological Characteristic Of Tridacnae

As a kind of biological-type organic gemstone,Tridacnidae belongs to tridacna families,eulamellibranchia, Veneroida, Mollusks Phylum. There are ten different species around the world of which six are in the water of our country. In this paper we study the structure and component of Tridacna from the perspective of gemology and biology,and choose Tridacna gigas as the main studying object,using EPMA, LA-ICP-MS, XRD powder diffraction,protein hydrolyzed amino acid analysis method,thermogravimetric analysis to analysse inorganic compound and organic compound in Tridacnidae;using SEM and other methods to observe the surface and inside structure;studying FIR spectrum and Raman spectrum of aragonite of Tridacna.Linking EPMA to XRD,this paper finds that the main inorganic compound in Tridacnidae is aragonite.Combining with thermogravimetric analysis,the content of aragonite is calculated between 90%-97%. The gray layer with higher transparency has the highest content of organic matter which up to 9%. White layer with lower transparency has the lowest content of organic matter which low to 3%. Yellow back adductor scar has medium content which is about 5%.Through LA-ICP-MS this paper finds that besides the major element calcium, sodium is the highest in content and is obviously higher in the back adductor scar than other places. Potassium is higher in inner layer of shell, which is latter formulated. Strontium, which is lower than calcium and sodium, is a little bit higher in the outside of R District.Using protein hydrolyzed amino acid analysis method, this paper finds that soluble protein has a obvious higher content in the back adductor scar(H) than district R around ligament and then central zone(Z) in the inside of mantle scar. Among them, the amino acids of components in H,R,Z are consistent but with different proportion. The ratio of acid to alkali on amino acid is highest in H, and lowest in R.Using SEM and other methods to observe the surface and inside structure, this paper finds that in the tridacnidae, only muscle prism in the back adductor scar is arranged in one direction, other muscle prism is staggered fold of which the unit is composed by tertiary structure. Aragonite structure layers with different transparency have different content of organic matter. High transparency means lower grow-up speed, more organic matter, more ordered arranged mineral grains and smaller lacuna. While lower transparency means higher speed of grow up, higher content of aragonite, stagger grains and bigger lacuna.According to the FIR spectrum and Raman spectrum of aragonite of Tridacna, the FIR spectrum shows the 699,712,1080 and 860 cm-1 peaks and the Raman spectrum shows 152, 207, 702, 1085,1460cm-1 peaks which have blue move and red move to different degree.