Occhi di Gatto

Ho trovato su un sito di gioielleria in inglese un articolo interessantissimo su una bella varietà di Pietra di Luna denominata Cat’s Eye Moonstone, ovvero Pietra di Luna Occhio di Gatto, e quindi ve lo traduco. Il gatteggiamento è un fenomeno ottico comune a varie pietre, la più famosa delle quali è l’Occhio di Tigre, una varietà di diaspro (famiglia di quarzi non trasparenti).

In calce all’originale potete trovare gli articoli relativi alle altre pietre che esibiscono questo spettacolare fenomeno. Più avanti magari li tradurrò.

Link originale: Cat’s Eye Moonstone

Pietra di Luna Occhio di Gatto
Foto dall’articolo

Storia e Introduzione

La Pietra di Luna Occhio di Gatto è una varietà da trasparente a opaca del feldspato ortoclasio noto come Pietra di Luna, un silicato di potassio e alluminio che esibisce il raro tratto del gatteggiamento (in inglese chatoyancy, NdT). Il gatteggiamento è un fenomeno ottico distinguibile da un unico riflesso della luce che somiglia molto alla pupilla di un gatto. È molto raro e capita solo in una manciata di gemme diverse, che comprendono il crisoberillo occhio di gatto, l’apatite occhio di gatto, l’acquamarina occhio di gatto e la tormalina occhio di gatto. In aggiunta al gatteggiamento, la pietra di luna occhio di gatto esibisce il fenomeno ottico dell’adularescenza, che è quello per cui la pietra di luna è più conosciuta. L’adularescenza è meglio descritta come uno splendore latteo o un bagliore luminoso che sembra venire da sotto la superficie della pietra.

segue

Moonstone is the best-known gemstone quality potassium feldspar. Its name is owed to the almost magical, bluish-white shimmer that resembles that of the moon at night. The shimmer is the result of alternating layers of orthoclase and albite which causes interference of light as it enters the stone. The light is reflected back and scattered equally, resulting in a fantastic schiller. The resulting sheen most commonly occurs in white, blue or blue-orange color and it appears with the cat’s eye reflection. The combination of adularescence and chatoyancy in a single stone is exceptionally rare. Top quality specimens can exhibit ‘three-dimensional’ depth of color due to moonstone’s remarkable level of adularescence.
Identifying Cat’s Eye Moonstone
Cat’s eye moonstone can be identified from other moonstone varieties by its chatoyancy. Since it is a potassium aluminum silicate, it can be easily identified through composition as well. Other gems with a similar appearance do not typically have the phenomenal presence of adularescence, which makes identification fairly easy. Testing for hardness is the easiest method to identify cat’s eye moonstone from other similar materials. Most other materials are either harder (cat’s eye quartz) or softer (cat’s eye apatite).

Cat’s Eye Moonstone Origin and Gemstone Sources
Cat’s eye moonstone is an extreme rarity, that occurs in the same mines as other varieties of moonstone. The most important deposits are sourced from Sri Lanka and India. Sri Lanka is most famous for its highly desirable bluish colored moonstone and India is the leading source for ‘blue-sheen moonstone’. Other notable deposits include Australia, Brazil, Myanmar (Burma), Madagascar, Mexico, Norway, Switzerland, Tanzania and the United States.
Cat’s Eye Moonstone Color
Moonstone is typically colorless, but it can actually occur in a wide range of colors. It most often occurs with a silvery sheen and base body colors of gray, cream, mocha, brown, yellow, orange, green, pink, blue and white. The most desirable moonstones are those with a blue sheen and a white to colorless body color. Deep-blue moonstone is the most valuable.

Cat’s Eye Moonstone Clarity and Luster
Cat’s eye moonstone typically occurs with translucent clarity when held to the light. Transparent specimens are most valuable. Cat’s eye moonstone has an attractive vitreous to pearly luster. Some rare moonstone gems may exhibit asterism, and are known as star moonstone. Star moonstone is exceptionally rare and highly desirable.

Cat’s Eye Moonstone Cut and Shape
Cat’s eye moonstone is always cut en cabochon. Cabochons maximize the desirable effects of chatoyancy. The orientation of cut is also very important in order to maximize the effects of schiller and adularescence, so most stones are cut with high domes. Cat’s eye moonstone is most often cut in ovals, since these shapes tend to preserve the most carat weight. Specimens with clear and distinct ‘eyes’ are considered most valuable.

Cat’s Eye Moonstone Treatment
Cat’s eye moonstone is not treated or enhanced in any way. However, there have been reports of some brighter blue colored moonstones being coated for color-enhancement.

Cat’s Eye Moonstone Gemological Properties:
Chemical Formula: KalSi3O8, Potassium aluminum silicate
Crystal Structure: Monoclinic, prismatic
Color: Colorless, yellow, pale sheen
Hardness: 6 to 6.5 on the Mohs scale
Refractive Index: 1.518 to 1.526
Density: 2.56 to 2.59
Cleavage: Perfect
Transparency: Transparent to translucent
Double Refraction or Birefringence: -0.008
Luster: Vitreous to pearly
Fluorescence: Weak; bluish, orange
Please refer to our Gemstone Glossary for details on gemology-related terms.

Cat’s Eye Moonstone: Varieties or Similar Gemstones:
Cat’s eye moonstone belongs to the large family of feldspar minerals. The feldspar minerals are the most abundant minerals on earth. In fact, approximately 60% of the Earth’s crust is composed of feldspar, which means there are a variety of related gems and minerals. Feldspars are typically classified into two main gemstone groups: Potassium feldspars and plagioclase feldspars.

All varieties of moonstone are potassium feldspars. Other potassium feldspars include amazonite and orthoclase. There are also several gemstones that are often confused with moonstone based on appearance, including ‘rainbow moonstone’. Rainbow moonstone is actually not a moonstone, rather, it is a variety of labradorite (plagioclase feldspar).

Most Popular Similar or Related Trade Names & Gemstones:
Moonstone, star moonstone, rainbow moonstone and sunstone are the most popular and well-known trade names used for similar or related gemstones.

Lesser-Known Similar or Related Trade Names & Gemstones:
Orthoclase, amazonite, labradorite, andesine, andesine-labradorite and oligoclase are the lesser-known trade names used for similar or related gemstones.

Cat’s Eye Moonstone Gemstone Mythology, Metaphysical and Alternative Crystal Healing Powers
Cat’s eye moonstone shares the same legend, powers and energy as other varieties of moonstone. Few gemstones have accumulated as much lore as moonstone. Moonstone has been known and revered for thousands of years by many cultures. According to Hindu legend, moonstone was formed from moonbeams, and at one time it was believed that if you held one in your mouth during a full moon, you would see your future. In India, moonstone is regarded as a sacred stone and it is widely believed to bring good fortune. In Arab countries women often sew moonstone into their garments, because it’s considered to promote fertility.

In ancient Rome, moonstone was associated with the moon and it was speculated that the gem was formed from drops of moonlight. The gemstones were believed to possess the properties traditionally associated with the moon, which include legend of romance, femininity, intuition, dreams, emotion and love. Moonstone is highly prized among lovers as it is thought to arouse tenderness and passion. Those who possess moonstone are thought to be able to foretell their future life together as a couple. Moonstone is the official birthstone for June. Moonstone is associated with the zodiac sign of Pisces. Physically, moonstone is thought to alleviate the symptoms and pain associated with headaches and common muscular backaches.
Cat’s Eye Moonstone Gemstone and Jewelry Design Ideas
Cat’s eye moonstone is not as hard as most other types of jewelry gemstones. Despite lack of durability, it remains one of the most popular gemstones for jewelry. In fact, moonstone has been worn as jewelry for centuries, dating back to ancient Greek and Roman civilizations.

Moonstone jewelry should be limited to protective-style jewelry designs, such as earrings, pendants, pins and brooches. Cat’s eye moonstone can be worn as a ring, but care should be taken to prevent scratches and blows. The wearing of cat’s eye moonstone rings should be limited only to occasional wear. Cat’s eye moonstone is extremely sensitive to pressure, so care should be taken when setting stones. Cat’s eyes are quite popular for both men and women. For men’s designs, cat’s eye moonstone is especially attractive as cufflinks and tie-tacks.

Note: Buy colored gemstones by size and not by carat weight. Colored stones vary in size-to-weight ratio. Some stones are larger and others are smaller than diamond by weight in comparison.

Cat’s Eye Moonstone Gemstone and Jewelry Care and Cleaning
How to clean your gemstonesCat’s eye moonstone is not very hard compared to other more popular types of jewelry gems. Therefore, quite a bit of care should be taken to retain the beauty of your cat’s eye moonstone gems and jewelry. Do not use any harsh chemicals or cleaners, such as bleach or sulfuric acid to clean your gems. Avoid the use of ultrasonic cleaners or steamers as well. To clean your gems, you can use a mild soap or detergent and simply wipe down your stones using a soft cloth. Be sure to rinse your gemstones and jewelry well with warm water to remove any soapy film and residue as this can dull the attractive luster of moonstone.

Moonstone is sensitive to pressure, so avoid extreme temperature and climatic fluctuations when possible. Do not set your gems in any type of tension-style mountings. Always remove jewelry before exercising, playing sports or performing household chores. When storing your cat’s eye moonstone gems, store them separately from other types of gems and jewelry. If possible, wrap stones individually in a soft cloth, or place them inside a fabric-lined jewelry box.

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