缅甸“有点咸”根珀与波罗的海蜜蜡的显微特征对比及意义

Micro-Characteristic of "Briny" Root-Amber from Myanmar versus Beeswax-Amber from the Baltic Sea and Their Significance

  • 摘要: 缅甸“根珀”是缅甸琥珀众多品种中的一类,其珀质油润、半透明-不透明,纹理多样,虽类似树根,但大多数没有树纹或者树木年轮的规律样式,故其样式及身世常给人们以神秘之感。通过扫描电子显微镜分析初步发现缅甸根珀内部近表面存在圆球形气孔,其直径变化在0.1~1.5 μm之间,气孔所占体积百分数约为6% vol.。几乎在每个气孔内部,都发现含有一个立方体状NaCl晶体。上述特征说明形成琥珀的树脂可能曾经处于一个确定的高气温、高盐度环境,为其所处潟湖环境提供了重要依据。缅甸根珀的内部气泡特征与波罗的海蜜蜡的内部气泡特征有一定的相似性,但其透明度明显逊于后者。波罗的海白色蜜蜡中的气泡直径为0.1~0.3 μm(气孔占7% vol.),尺寸远小于细小微粒直径1.0 μm。微粒直径1.0 μm对应于12 500目,这个粒径级别的粉尘,若为透明矿物,其颜色表现为白色。借助透明矿物条痕色基本为白色的原理,我们认为白色蜜蜡的颜色是由直径极小(100~300 nm)〖JP2〗的密集气泡所呈现的白色,并非真实琥珀物质颜色,并将此确定为白色蜜蜡现象。缅甸根珀的呈色机理与波罗的海白色蜜蜡区域有一定可比拟性,其更低的透明度可能归因于内部还包含岩盐晶体。白色蜜蜡中直径细小且密集(气孔占约7% vol.)的气泡特征,很好地解释了在摩擦时,白珀更容易散发琥珀气味的现象,因为在摩擦时,这些细密的气泡很容易爆破并释放其中气味。黄色蜜蜡中气泡直径较大(5.0~10.0 μm),且气孔占体积百分数(约1% vol.)较低,进一步验证了气泡对透明度产生了明显影响的认识,但对其体色并未产生明显影响。综合以上特征,或许将缅甸“根珀”更名为“根蜜蜡”更为合适。

     

    Abstract: Root-amber is one of the many varieties of amber from Myanmar, which is translucent to opaque with greasy lustre. Although the varied textures resemble tree roots, most amber lack of the regular tree patterns or annual rings. Thus, its pattern and origin often leave people with a sense of mystery. Preliminary analysis by scanning electron microscope revealed the presence of rounded spherical bubbles on the internal surface of root-amber from Myanmar, which varied in diameter from 0.1 μm to 1.5 μm, and the percentage of volume occupied by the bubbles was about 6% vol. A cubic halite crystal was found in almost every bubble inside. Features above suggest that the sap that formed the amber was once in a high temperature, high salinity environment, providing an important basis for the lagoon environment in which it was preserved. Such characteristics of bubbles in Myanmar root-amber share some similarities with Baltic beeswax-amber in terms of internal characteristics, but its transparency is significantly inferior to that of the latter. The diameter of the bubbles in Baltic white beeswax-amber ranges from 0.1 μm to 0.3 μm (pores account for 7% vol.), which is much smaller than the fine particles of 1.0 μm in diameter. One micron corresponds to 12 500 mesh, which reaches the particle size level of dust that presents white colour if the mineral is transparent. According to the principle that transparent mineral streaks are basically white, we believe that the white colour of the white beeswax amber is presented by the dense air bubbles of very small diameter (100-300 nm), not the real amber substance colour, and identify this as the white beeswax-amber phenomenon. The mechanism of coloration of root-amber from Myanmar is partially comparable to that of white beeswax-amber from Baltic, and its lower transparency may be attributed to the NaCl crystals that also contained inside. The discovery of small and dense (about 7% vol.) bubbles in white beeswax-amber also explains why white beeswax-amber is more readily able to release its rosin odor when it is rubbed, as these fine bubbles burst easily and release their odor when rubbed. The larger diameter (5.0-10.0 μm) and lower density of bubbles (about 1% vol.) in yellow beeswax-amber suggest that the bubbles only have a significant effect on its transparency and not on its body colour. Combining the above characteristics, it is suggested that it is probably more appropriate to change the name of Myanmar "root-amber" to "root beeswax-amber".

     

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