黑玛瑙 Onyx
玛瑙的主要成份都是SiO2（二氧化硅），质地很纯时为灰色，若含有色素时便呈现红、黑、蓝、绿等各色。玛瑙一般呈透明到不透明，硬度6.5至7度，比重2.55至2.91，折射率1.535至1.539。世界最著名的黑玛瑙产地有印度、巴西等地。
The main ingredients of Onyx are SiO2. The color is gray when the texture is pure. If they contain varies of pigment, they will show red, black, blue, green and so on. Generally, onyx is transparent to translucent, hardness is 6.5-7.0, the proportion is 2.55 to 2.91, the refractive index is 1.535 to 1.539. The most famous origins of Onyx in the world are India, Brazil and other places.
