The so-called “opal stone” in gemology refers specifically to golden emeralds with cat’s eye effect. Any other gem mineral with cat’s eye effect cannot be called “opal stone” in general, but must be in front of its name. It is given mineral names, such as “emerald cat’s eye” または “quartz cat’s eye”.
The chemical composition of gold emerald is beryllium aluminate (BeA12 04), the crystal is columnar or plate, and can have several varieties such as brown and greenish yellow; it is glassy luster, hardness 8.5, density 3.73g/cm3; shell Shaped fracture, white streaks, when it has densely aligned fibrous and needle-like mineral inclusions or tubular holes inside
A bright band like a cat’s eye pupil will be produced due to the reflection of light, which is the cat’s eye effect. When the gem is rotated, this bright band will move on the surface of the gem, so it is also called “play-of-color”, which is the most important feature of opal.
Since the best opal (ie golden-green opal) is produced in Sri Lanka in the East, it is also called “Oriental Cat’s Eye” または “Sri Lankan Cat’s Eye” (formerly known as “Ceylon Cat’s Eye”).
According to incomplete statistics, among the more than 230 gems and jade minerals, より多い 20 are known to have the cat-eye effect, and this number is still increasing slowly. The names of these gem minerals with cat-eye effect are (except chrysoberyl):
Alexandrite opal (both discoloration and cat-eye effect, very rare and precious), ルビー, サファイア, エメラルド, トルマリン (トルマリン), アクアマリン, 石英, ジルコン, cassiterite, diopside, transparent Amphibole, moonstone, labradorite, かんらん石, actinolite, calcite, epidote, andalusite, enstatite, serpentine, apatite, wollastonite, iron ore, malachite cat’s eye Wait.