石榴子石是在每個大陸的變質岩與火成岩中發現的最常見和最廣泛的寶石之一。石榴石是正矽酸鹽家族的總稱。所有石榴子石的晶體結構基本相同，但化學成分不同。石榴子石的種類有二十多種，但只有六種在商業上作為重要的寶石。這六種是鎂鋁榴石，鐵鋁榴石，錳鋁榴石，鈣鋁榴石，鈣鐵榴石和鈣鉻榴石。石榴石的種類通常是根據其顏色外觀而非準確的化學分析方法來判定。但是，即使經驗豐富的寶石學家對於石榴子石的種類判斷依然會經常有偏差。
拉曼光譜技術是寶石學研究上必不可少的分析技術。拉曼現象是一種非彈性散射，基於光與材料內分子鍵的相互作用，用於判測分子的振動模式。拉曼光譜儀是大多數寶石學實驗室必備的工具，其分析是快速且無損的。
在這項研究中，我們測量天然矽酸鹽石榴子石群以及其固溶體，尤其關注鎂鋁榴石-鐵鋁榴石固溶體系列以及鈣鋁榴石-鈣鐵榴石固溶體系列的單晶拉曼光譜。能量色散X-射線光譜儀（EDS）將用於樣本相應的化學成分分析。藉由收集拉曼光譜和化學成分的數據，定出鎂鋁榴石-鐵鋁榴石固溶體系列以及鈣鋁榴石-鈣鐵榴石固溶體系列當中各振動模波數與主成分的關係方程式。除了可以對各系列的石榴子石進行種別的劃分外，也可以藉以判定成份未知的硅酸鹽石榴子石的半定量化學組成。更重要的是，經由每個寶石實驗室中都配置的無損拉曼光譜測試來推測石榴子石之對應化學成分，將成為極為方便且低成本的石榴子石及其它固溶液寶石之鑒定程序。

Garnet is one of the most common and widespread gemstones found in metamorphic and volcanic rocks on every continent. The crystal structure of all garnet is basically the same, but the chemical composition is quite different. There are more than twenty types of garnets, but only six are commercially important gems, namely almandine, grossular, andradite, uvarovite, spessartine and pyrope. The identification of garnet species is usually determined by its color and appearance rather than by accurate chemical analysis, but even experienced gemologists can often be wrong about the identification of garnet species.
Raman spectroscopy is an indispensable analytical technique in gemological research. As an inelastic scattering effect, Raman signals results from vibration mode of molecules based on the interaction between light and the molecular bonds in the material. The Raman spectrometer is an essential tool in most gemological laboratories and its analysis is rapid and nondestructive.
The study aims to provide reliable experimental data of silicate garnet by non-destructive, efficient Raman spectroscopy testing. The single crystal Raman spectra of natural silicate garnets with compositions close to end-member almandine, grossular, andradite, uvarovite, spessartine and pyrope along with the Raman spectra of their solid solutions are measured. Energy Dispersive Spectrometer (EDS) will be applied for corresponding chemical composition analysis on each specimen studied. We found that most of the wavenumber of Raman modes show linear relationship with major component of garnet. Our results can provide reliable way of determining mineral species of garnet group, especially pyrope-almandine and grossular-andradite binaries. Moreover, the chemical composition of major elements can also be semi-quantitatively determined. It is promising that Raman spectroscopic method can be adopted in all gemological laboratories for the quick and non-destructive determination of mineral species of garnets and other gemstones of solid solution.

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