The beryl gemstone means the beryl gemstones of various Colors（色） except the aquamarine and emerald. The beryl often takes on different Colors（色） due to the content of trace and tiny transitional element. The mains types are as follows:

(1)    Golden beryl: It is a kind of transparent crystal of beryl, taking on yellow, golden または light オレンジ yellow color. The reason of coloration is that there is iron in the chemical element. The refractive index is 1.570 – 1.575 and the birefringence is 0.005. It has polychroism, from weak green yellow to yellow. The Mohs hardness is 7.5 and...