1. The main feature of opal is that it can see a clear brown cat's eye. The spun silk inclusions of opal are rutile and hollow tube. Because these tubular inclusions are slender and dense, the cat's eye effect is particularly obvious even under weak light source.

2. Artificial opal is made of glass fiber, which is red, blue and brownish yellow, and some brownish yellow varieties are very similar to natural opal. The difference between the two is that artificial opal has 2-3 bright bands at the arc top, while natural opal has only one; Observing the two sides of artificial opal with a magnifying glass, we can see the hexagonal honeycomb structure; Meanwhile, the hardness of artificial opal is lower than that of natural opal.

3. Illuminating from the side of the opal with a single light source, the colors on both sides of the opal are different. When the honey yellow opal is illuminated from the left, it is honey yellow on the left and milky white on the right. When illuminated from the right, its color is just the opposite.

Cat's eye, that is, "golden emerald with cat's eye effect". Also known as "cat's eye", "cat's eye", "cat essence" and oriental cat's eye, it is a rare and precious variety in jewelry, also known as Alexander's cat's eye, which has both discoloration and cat's eye phenomenon.

Opal is one of the rarest and most precious emeralds. Only Sri Lanka is produced in the world, and the price is quite expensive. /kloc-It's hard to see domestic shopping malls above 0/0 carat. Opal is named because it is as flexible and bright as a cat's eye and can change with the intensity of light. This optical effect is called "cat's eye effect".