How is the opal formed? Let's let Xiaobian introduce the formation of the opal for everyone!
Strictly speaking, "cat's eye" is not the name of a gem, but an optical phenomenon on certain gemstones. That is, when a gemstone that has been ground into a hemispherical shape is illuminated with strong light, a thin and bright reflection will appear on the surface, which is called "cat's eye flash" or "cat's eye light", and then it is named according to what the gem is. If the gem is quartz, it is called "Quartz Cat Eye", if it is a gold emerald, it is called "Golden Green Cat Eye." There may be many types of gemstones that may have a cat's eye flash. According to statistics, there may be as many as 30 kinds. In addition to the quartz cat's eye and the golden-green cat's eye, there are mainly "Gemstone Cat's Eye" and "Aquamarine Cat's Eye". Because the golden green cat's eye is the most famous and most precious, it is also referred to as "cat's eye" in the habit. Other cat eyes cannot be called.
Opal belongs to Chrysoberyl in mineralogy and belongs to the gold emerald mineral. Opal has a variety of colors, such as honey yellow, brown yellow, wine yellow, brown yellow, yellow green, yellow brown, gray green, etc., among which honey yellow is the most expensive. Transparent to translucent. Glass to grease luster. The refractive index is 1.746-1.755, and the birefringence is 0.008-0.010. The dichroism is obvious, the dispersion is 0.015, and it is heterogeneous. Hardness 8.5, density 3.71-3.75 g / cm3. Shell-shaped fracture. The difference between opal and other similar gemstone cat eyes and artificial cat eyes.
Gems that produce cat's eye effect in nature include tourmaline, beryl, apatite, quartz, and kyanite, but they are not as precious as gold-green cat eyes. Tourmaline cat's eye: the hardness is small, 7-7.5, density 3.06 g / cm3, refractive index 1.624-1.644. Quartz cat's eye: low hardness, about 6.5, low density, 2.78 g / cm3, low refractive index, 1.44. Artificial cat's eye: Opal made of artificial glass fiber, brownish yellow, blue and red. However, the artificial opal has 2-3 bright bands at the top of the curved shape, and only one bright band appears in the natural opal. Observed by a magnifying glass, the artificial opal has a hexagonal honeycomb structure with a low hardness of about 5, a low density of 2.46 g/cm 3 and a refractive index of 1.44.
The above introduces how the opal stone is formed. By introducing everyone to know more about the opal, I hope that this knowledge can help you.
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