Is the opal a luminous pearl?

Opal is one of the important varieties of the emerald family. The hardness is 8.5 degrees, second only to diamonds, rubies and sapphires, and the colors are mostly honey yellow, yellow brown, yellow green, green white and coffee, all of which have obvious golden tones, hence the Chinese name. A good opal, the bright line of its cat's eye is located in the center of the arc surface of the gem, narrow and clear, and presents a vivid light. Opal is very precious because of its special light effect. High-quality opal over 10 carat can be worth millions of dollars. The method of identifying the authenticity of opal is as follows:

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. This is unmatched by other gems.

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

3. 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.