摘要
本文收集了产自埃塞俄比亚的绿黄色琥珀原石样品,对其宝石学特征和谱学特征进行了测试分析。测试结果表明,埃塞俄比亚琥珀的折射率为1.54~1.55(点测),密度为1.022~1.058 g/cm^(3),长波紫外线下琥珀基体呈强蓝白色荧光,褐红色氧化层呈中等强度绿色荧光,显微镜下可见琥珀中具有水胆、气泡、黑色团絮物、“翅果”状包体等内含物,以及由树脂多期次堆覆导致的层状或波状纹理;红外光谱和拉曼光谱均呈现琥珀典型的脂肪族基团和氧化基团的组合,同时也含有少量不饱和组分,振动谱带峰位特征与豆科植物的石化树脂较为相似;拉曼光谱中指示琥珀成熟度的I_(1650 cm^(-1)/1442_cm^(-1))值落在0.69~0.75范围,与多米尼加琥珀接近;绿黄色埃塞俄比亚琥珀的紫外-可见-近红外光谱具以630 nm为中心的平缓吸收宽带,是其绿色调的主要成因。
Specimens of greenish-yellow amber from Ethiopia were collected and tested for their gemmological and spectroscopic characteristics.The test results showed that amber from Ethiopia has a refractive index of 1.54-1.55(point measurement)and a density of 1.022~1.058 g/cm 3.Wave-like anomalous extinction was visible under crossed polarizer.The amber matrix showed a strong blue fluorescence under long-wave ultraviolet light,while after a long period of natural oxidation in the air,the fluorescence turned to blue-green with a slightly lower intensity.The maroon oxidized surface showed a green fluorescence in medium intensity.In the transitional zone from the oxidized surface to the inner matrix,the body colour showed gradient transition from brownish red to yellow,however the long-wave ultraviolet fluorescence image showed a clear boundary of the transitional zone.Observed by microscope,the amber contained inclusions such as gas-liquid two-phase inclusions,gas bubbles,black flocs,“samara-like”inclusions,and lamellar or wave-like patterns caused by multiple stages of resin accumulation.Both IR and Raman spectra showed a combination of aliphatic and C=O functional groups typical of amber,with small amount of unsaturated components.The vibration spectral characteristics were similar to those of fossilized resins from Leguminosae plants.The value of I_(1650 cm^(-1)/1442 cm^(-1)) in the Raman spectra indicating the maturity of amber fell in the range of 0.69-0.75,which was rather close to that of amber from Dominica.The UV-Vis-NIR spectra of greenish-yellow amber from Ethiopia showed a broad band centered at 630 nm,causing the unique greenish tint of its body colour.
作者
招博文
吕晓瑜
支颖雪
代荔莉
吴嵩
郑雨佳
ZHAO Bowen;LYU Xiaoyu;ZHI Yingxue;DAI Lili;WU Song;ZHENG Yujia(Shanghai Institute of Measurement and Testing Technology,Shanghai 200233,China;Antwerp Laboratory for Gemstone Testing,Antwerp 2018,Belgium;Beijing Youzhuju Network Technology Co.,Ltd.,Beijing 101200,China)
基金
上海市市场监督管理局科技项目(I00RJ2215)。
