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By Reviewed By Andreas Zabczyk

Star Moonstone Gemstone Information and Education

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About Star Moonstone - History and Introduction

Star moonstone is a gem quality variety of orthoclase feldspar, a potassium aluminum silicate known as moonstone which exhibits a rare asterism effect under specific lighting. When viewing star moonstone, a four-rayed star will appear to float across the surface of the stone. The effect is best viewed under a direct light source and while tilting, rotating and viewing the stone from different angles. In addition to its rare asterism, star moonstone is known to exhibit adularescence, an optical trait that moonstone is particularly known for. Adularescence is best described as a milky sheen or a wavy glowing light which appears to come from below the surface.

Moonstone owes its name to the almost magical, bluish-white shimmer that closely resembles the appearance of the moon. The shimmering sheen 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 four-rayed star. The combination of adularescence and asterism in a single stone is exceptionally rare. Top quality specimens can exhibit a 'three-dimensional' color, owing to moonstone's remarkable level of adularescence. Some rare gems may exhibit a cat's eye effect (chatoyancy) rather than asterism, and are known as cat's eye moonstone gems. Cat's eye moonstone is exceptionally rare and highly desirable.

Star Moonstone Gemstone

Identifying Star Moonstone

Star moonstone can be identified from other moonstone through its asterism. Star moonstone is potassium aluminum silicate and it can be easily identified by its composition. Other gems with similar colors lack the phenomenal presence of adularescence, which makes the identification of star moonstone fairly easy. Scratch testing for hardness is often one of the most common methods for identifying star moonstone from other similar star gemstones. Other star gems are typically significantly harder (star rose quartz) or significantly softer (star diopside) than star moonstone. Star moonstone also exhibits straight four-rayed stars at near-perfect right angles. The four-rayed stars exhibited by star diopside are often wavy and do not intersect at right angles. Star ruby and star sapphire exhibit six-rayed stars.

Star Moonstone Origin and Gemstone Sources

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Moonstone deposits often occur as constituents in feldspar-rich granitic and syenitic pegmatites. Star moonstone is extremely rare, occurring in the same mines as moonstones. The most important deposits are from Sri Lanka. Other notable star moonstone sources include Australia, Brazil, Germany, Myanmar (Burma), Madagascar, Mexico, Norway, Switzerland and Tanzania. Today, Sri Lanka is known to produce a highly desirable blue colored moonstone and India is the number one source for blue-sheen moonstone, otherwise known as 'rainbow moonstone'.

Buying Star Moonstone and Determining Star Moonstone Gemstone Value

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Star Moonstone Color

Star moonstone is typically colorless, but it can actually occur in a wide range of colors. It most often occurs with a silvery sheen with base body colors of gray, mocha brown, yellow, orange, green, pink, blue, cream and white. Star moonstone with blue sheen and white to colorless body color is most desirable. Deep-blue is considered the most valuable.

Star Moonstone Clarity and Luster

Star moonstone is typically milky and translucent when held to the light. Transparent specimens are most valuable. Star moonstone has an attractive vitreous luster when cut and polished. Specimens with well-centered and clear, distinct stars are considered most valuable.

Star Moonstone Cut and Shape

Star moonstone is always cut en cabochon in order to maximize the desirable asterism and adularescence. With star moonstone, orientation of cut is very important in order to maximize the sheen of moonstone. Almost all star moonstone is cut with very high domes and in oval shapes, because ovals tend to preserve as much of the rough carat weight as possible. Round stones and calibrated sizes are extremely rare and can demand high premiums.

Star Moonstone Treatment

Star moonstone is not known to be treated or enhanced in any way, although some blue colored moonstones have been reported as color-enhanced by 'coating'.

Star Moonstone Gemological Properties:

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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 of gemology-related terms.

Star Moonstone: Varieties or Similar Gemstones:

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Moonstone Cabochon
Moonstone Cabochon

Star moonstone belongs to the feldspar group of minerals. Feldspars make up approximately 60% of the Earth's crust, making them the most abundant mineral on earth. Feldspar gemstones are classified into two main branches: Potassium feldspar and plagioclase feldspar. Star moonstone is a potassium feldspar, which also includes lesser-known stones like amazonite and orthoclase.

'Rainbow moonstone' is a very similar gemstone, but it is actually not a 'moonstone' at all. Despite its name, it is a variety of labradorite, which is plagioclase feldspar, not potassium feldspar. Even so, since they are both varieties of feldspar, so they are very closely related. 'Rainbow moonstone' is sometimes referred to as 'blue-sheen labradorite', which is technically a more appropriate trade name.

Most Popular Similar or Related Trade Names & Gemstones:

Moonstone, cat's eye moonstone, rainbow moonstone and sunstone are the most popular and well-known similar or related gemstones.

Lesser-Known Similar or Related Trade Names & Gemstones:

Orthoclase, amazonite, andesine, labradorite, andesine-labradorite, blue sheen labradorite and oligoclase are lesser-known similar or related gemstones.

Star Moonstone Gemstone Mythology, Metaphysical and Alternative Crystal Healing Powers

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Star moonstone has all of the same legends, powers and energy as other varieties of moonstone. Few gemstones have accumulated as much lore as moonstone. According to Hindu legend, moonstone was formed from moonbeams. In India, moonstone is regarded as sacred and it is widely believed to bring good fortune. In many Arab countries, women are known to sew moonstone into their under-garments, as it is considered a symbol of fertility.

In ancient Rome, moonstone was believed to have been formed from drops of moonlight. It was believed to harness the power of the moon, including legends of romance, dreams, emotion, femininity, intuition and love. Moonstone is highly prized among lovers, as moonstone is believed to arouse tenderness and passion. Many cultures believe moonstone to be an excellent healing stone and it is thought to be able to alleviate pain and symptoms associated with headaches and common backaches. Moonstone also has a historical connection with travelers and dwellers, in fact, it was once known as the "traveler's stone".

All varieties of moonstone are official birthstones for June and they are associated with the zodiacal sign of Pisces.

Disclaimer: Metaphysical and Alternative Crystal Healing Powers and Properties are not to be taken as confirmed advice. Traditional, Ceremonial and Mythological Gemstone Lore is collected from various resources and is not the sole opinion of SETT Co., Ltd. This information is not to replace the advice of your doctor. Should you have any medical conditions, please see a licensed medical practitioner. GemSelect does not guarantee any claims or statements of healing or astrological birthstone powers and cannot be held liable under any circumstances.

Star Moonstone Gemstone and Jewelry Design Ideas

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Star moonstone is not as durable as most other jewelry gemstones. However, despite its fragility, it remains very popular for jewelry designs.

Star moonstone is always cut en cabochon, so jewelry designs are limited to those that can accommodate flat bottoms. The wearing of star moonstone should be limited to protective-style jewelry, such as pendants, earrings, pins or brooches. Star moonstone can make stunning cabochon gemstone rings, but extra care should be taken to prevent scratches and blows due to its softness. Star moonstone rings should only be worn occasionally. Star moonstone is also sensitive to pressure, so extra care should be taken while setting stones (avoid tension-style settings). Star gemstones are quite popular for both men and women. For men, star moonstone is especially ideal for cuff-links 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.

Star Moonstone Gemstone and Jewelry Care and Cleaning

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How to clean your gemstonesStar moonstone is not very durable. Therefore, it requires quite a bit of care, especially when worn as jewelry. Do not use harsh chemicals or cleaners to clean your gems, such as bleach and acid, and avoid the use of ultrasonic cleaners or steamers. Use only a mild soap or detergent and wipe down your stone using a soft cloth or brush. Be sure to rinse well using only warm to room temperature water to remove soapy residue.

Star moonstone is sensitive to pressure, so avoid extreme climate fluctuations if possible. Always remove star moonstone jewelry before engaging in exercise, physical sports or household tasks. When storing your star moonstone gems, keep them away from other types of gems and jewelry to prevent scratches. If possible, it is best to wrap your stones individually using a soft cloth, or place them inside a fabric-lined jewelry box for extra protection.

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