Study Of Gem-Quality Red Coral's Composition And Structure Characteristics

Gem-quality red coral is an important organic gem material.Fine specimens of attractive pink-to-red coral are the most desirable yet among the least available.These specimens are belonging to Anthozoa class,Octocorallia subclass,Alcyonacea order,Scleraxonia suborder, Coralliidae family in zootaxy.The Coralliidae family includes Corallium genus and Pleurocoralloicles genus.The concept of "precious red coral" is easily be confused by "red coral", "calcite-type coral","Corallium Cuvier genus".The previous researches always took "red coral" as research object resulted in the inaccuracy of objects'description.Therefore,define the category of gem red coral is the first principle of this study.Recent years,as the result of the increasing demand of the gem-quality red coral in jewelry market,the gem-quality red coral fishery develops rapidly.The new situation of the gem-quality red coral market has transferred from Italy to Taiwan province located in the west coast of Pacific Ocean.Meanwhile,many kinds of imitations of gem-quality red coral appear in the jewelry market, such as dyed Isis hippuris,Gilson coral.The market proposes a impending requirement to the gem-quality red coral research.Researches on the composition and structure characteristics of the gem-quality red coral are the basis of the further study on the color origin and biomineralization. This study is expanding surround these points above.The main research objects are three important genus of gem-quality red coral.They are Corallium rubrum(belonging to Corallium genus),Corallium elatius(belonging to Corallium genus),Corallium japonicutn(belonging to Pleurocoralloicles genus).The main contents are as following:1.This study takes the knowledge on biology,zootaxy,organic gemology in consideration, raising the concept of "gem-quality red coral" aimed at avoiding the confusion of "red coral" and other names.The study confines the colony of Coralliidae family as the gem-quality red coral,and takes Corallium rubrum,Corallium elatius,Corallium japonicum as main research objects. Furthermore,some imitations are also took as research objects.2.The study tests the samples by FTIR,Raman scattering measurement,UV-vis,XRD.The result of the FTIR shows the mineral component of gem-quality red coral is high-Mg calcite,while the mineral component of the Acropora millepora is aragonite.This phenomenon could not only be taken as the evidence to separate the biogenic calcite and mineral source calcite but also indicate the lattice distortion caused by organic matter.The spectrum peaks in the region 4000～2000 cm^-1representing the vibration function group indicate the existence of the organic matters in gem-quality red coral.The research uses the XRD data to calculate the cell parameter,cell volume,grain size of the gem-quality red coral and to conjecture the preferred orientation of the calcite grain.3.The research tests the quantity of the major elements and trace elements in different sections of the gem-quality red coral by electron microprobe and LA-ICP-MS.The result shows some element pairs are relative.Some subtle distinctions are found between three different varieties.The result deny the inference of coloring ions causing the color of gem-quality red coral. The GC-MS test analyses the organic matter separated and extracted from the Corallium elatius. The result shows the samples contain C16 and C19 aliphatic alcohol.4.The raman spectrums of the red part and the white part of the gem-quality red coral are different.The raman spectrum of the red part of the gem-quality red coral has some additional bonds representing the organic matters compared with the white part.In addition,the differences in spectrums are exist between the gem-quality red coral and the Isis hippuris.The spectrum of the Isis hippuris does not have the peaks in 1517 cm^-1,1296 cm^-1,1128 cm^-1,1016 cm^-1,but has a strong fluorescence background.Raman scattering measurement is a fast,nondestructive way to identify the natural gem-quality red coral.It is an effective method to reveal the relationship between the organic matter and color.5.Gem-quality red coral is a kind of important composite material made by organic matters and mineral crystal.The fraction of grain size could reach to micrometer or nanometer scale.This research describes the architecture type,micro structure,ultrastructure characteristics of gem-quality red coral and analyzes the characteristics of the organic framework and the inorganic substances.A novel approach of in situ analysis was constructed by means of decalcification, ion-milling combined with Scanning Electron Microscope(SEM),Transmission Electron Microscope(TEM)ultra-structure analysis and X-ray powder diffraction(XRD).The method was employed to determine the spatial distribution of organic framework,outside and inner crystal and organic/inorganic interface spatial geometrical relationship in Corallium elatius.The results show that there is a sub-structure of organic matrix in calcite crystal.Cavity templates are responsible for supporting,limiting size and shape and determining the crystal growth spatial orientation, while intracrystal organic matrix is responsible for providing nucleating point and induce nucleation process of calcite.The research reveals the distribution characteristics of the organic matter and inorganic matters spreading in the Corallium elatius.The result serves the bionics a new direction.The main innovation of this paper as follows:1.The definition of "gem-quality red coral" has been proposed for the first time.2.The research detects the organic matters which is related to the red color of the gem-quality red coral for the first time by Raman spectroscopy.The research analyses the number of the C=C bond and gets the conclusion that the color of the gem-quality red coral is caused by organic matter which containing polyenic chains of different lengths.The result supports the theory that the organic matters cause the color of gem-quality red coral.3.The research observes the gem-quality red coral samples from macroscopic to microscopic.This work make the structure of the sclerite and axis clearly.4.The research of the SEM observes the organic frame-work in the skeleton of the gem-quality red coral.The organic frame-work forms many 3-d cavities.The research involves the knowledge and the analytic methods of biology,mineralogy, petrology,taxology,gemology.The test methods of spectroscopy and micro analysis including organic chemistry and inorganic chemistry are comprehensive analysis.The cause of the color in gem-quality red coral is a frontier topic which has no verdict yet. The conclusion on the cause of the color in gem-quality red coral in this paper provides the basis information to optimization treatment.The research on the biomineralization is the hotspot in the field of bio-inorganic chemistry. The SEM test has found the 4 different types of spicule and multi-stage organic framework in the Corallium elatius for the first time.The study enrich the biomineralization data.This research as a basic research analyses three kinds of gem-quality red coral systematically, and fill the organic gemology with more data about the composition and the structure of the gem-quality red coral.