Gemstones can change like the eyes of a cat, accompanied by the intensity of light, flexible and bright, strange and mysterious, and fascinating. This optical effect is the "cat eye effect." The term opal has both broad and narrow meanings. In a broad sense, it refers to all gemstones with cat's eye effect, and narrowly refers to gold emerald cat eyes. In the broad sense, the opal needs to be pointed out to distinguish the gemstones, such as tourmaline cat eyes, moonstone cat eyes, apatite cat eyes, quartz cat eyes, glass cat eyes and so on.
1, gold emerald
Gold Green Cat's Eye is abbreviated as "cat's eye", the mineral name is gold emerald, the chemical formula is BeAl2O4, often contains trace elements such as iron, titanium, chromium; yellow, honey or green and brown, honey yellow is better, half Transparent; gold-green cat's eye density is 3.70-3.73g/cm3, refractive index is 1.73 or 1.74 (dot), hardness is 8.5, and part of the absorption line of 444nm is visible, which has important identification significance. The stone cat's eye is a rare gemstone that combines the cat's eye effect and color change. The discoloration is caused by the chrome element. The cat's eye effect is produced by the light reflected by the fine needle or tubular inclusion. Its physical properties and the golden green cat's eye. Roughly the same.
2. How do you produce cat eyes?
1) The gemstone contains a large number of parallel-arranged inclusions, or the gemstone is composed of fibrous, long columnar minerals in a certain direction. The inclusions may be gas-liquid inclusions, fibrous, needle-like crystals (such as rutile, tourmaline, etc.) or tubular, hollow (such as negative crystals, elongated bubbles, etc.) left by the crystal during growth, or A set of oriented cleavage lines in various seed crystals or gemstones.
2) The gemstone must be cut into a curved surface with the bottom surface parallel to the plane of the inclusion. If the two are not parallel (with a certain angle), the eyeliner position of the cat's eye is not centered or even disappears.
3. Where do you produce cat eyes?
Gold-green opal is mainly produced in gas-forming hydrothermal deposits and pegmatite veins. Because of its chemical nature, gem-quality gold-green cat eyes are often produced in sand mines, with scarce production and difficult mining. Sri Lanka is the main producing area of ​​the Golden Green Opal. The golden green cat eyes produced in the southern part of Sri Lanka, such as Tranabula and Gore, are also cherished by the world. Russia's Ural Mountains were famous for producing golden-green cat eyes, and later the output declined. Golden green opal is also produced in Brazil, Myanmar, and Zimbabwe. The beautiful meaning and rare production make the Golden Green Cat Eye one of the top five high-end gemstones in the world.
4. How to choose?
In addition to the evaluation of the impact of the gemstone itself, the evaluation of the opal must also consider the appearance of the cat's eyeliner. The evaluation is mainly reflected in five words: positive, straight, thin, live and bright.
Positive: The cat's eyeliner should not be skewed, and it is better to traverse the long axis of the ellipse. It is more beautiful in proportion.
Straight: The cat's eyeliner should be straight, and if it is twisted or bent, it will affect its aesthetics.
Fine: The thinner the cat's eyeliner is, the better. Generally speaking, the thickness of the cat's eyeliner is related to the thickness of the fibrous and tubular structure. In the processing, when the surface curvature of the convex gemstone is high, the bright band is narrow and clear.
Live: The cat's eyeliner should be flexible. If the opal is slightly shaken, the cat's eyeliner will move with the angle of the light source, presenting a vivid "cat's eye".
Bright: The brighter the cat's eyeliner is, the better the opal is. The fiber optic structure is not dense enough or the development is not good, and the eyeliner is dim. If it is not bright, it is not obvious, so the value is lower.
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