What Is Moonstone Gemstone?
Moonstone is a sodium potassium aluminium silicate of the feldspar group that displays a pearly and opalescent schiller. An alternative name is hecatolite.
The most common moonstone is of the orthoclase feldspar mineral adularia, named for an early mining site near Mt. Adular in Switzerland, now the town of St. Gotthard. Solid solution of the plagioclase feldspar oligoclase +/- the potassium feldspar orthoclase also produces moonstone specimens.
Its name is derived from a visual effect, sheen or schiller (play of color), caused by light diffraction within a micro-structure consisting of regular exsolution layers (lamellae) of different alkali feldspars (orthoclase and sodium-rich plagioclase).
What is the chemical formula for Moonstone?
((Na,K)AlSi3O8)
How Is The Moonstone Formed?
Moonstone is a variety of the feldspar-group mineral orthoclase. It’s composed of two feldspar minerals, orthoclase and albite. At first, the two minerals are intermingled. Then, as the newly formed mineral cools, the intergrown orthoclase and albite separate into stacked, alternating layers.
What Are The Different Types and Colours of Moonstone?
Types of Moonstone
Blue Moonstone
Blue moonstone is transparent and crystal clear with a floating blue tone on the surface.The most desirable stones have the most intense blue colour. The largest and best stones have traditionally come from Myanmar(Burma), however it has become much harder to find good stones and therefore the price has increased.
Rainbow Moonstone
Rainbow moonstone has a milky patchy appearance which comes from the white orthoclase inclusions and layers. When the stone catches the light, the reflection off the layers and inclusions produces a rainbow effect. The colour play has made this a very popular stone and it is often used in silver jewellery.
The scientific name for rainbow moonstone is labradorite, and despite the name it is different from true moonstone, which is called orthoclase.
Green Moonstone
Green moonstone is not as well known as rainbow or blue moonstone as it does not have the colour play, however it is still a beautiful stone. It usually has a slightly hazy or clear appearance an a pale green-yellow colour. When you look down at the stone you will see a light emanating from within, like a full moon. It is commonly cut with a high dome to accentuate this optical effect and frequently a star of light will be visible on the top of the dome.
Pink Moonstone
The term pink covers colours from honey to beige to peach, ranging from translucent to opaque. The stone should have a white sheen and is often found with a cat’s eye or star effect. This type of stone is often used in rows of coloured beads.
Orthoclase
Orthoclase is a relatively inexpensive transparent stone that is colourless or pale yellow, and can have a blue white tone or sheen. The colourless variety is called adularia, as it was found at Mount Adular in Switzerland. Orthoclase is commonly faceted as a step cut due to its fragile nature, and becasue of this it is not widely used or produced.
Amazonite
Amazonite is an attractive opaque stone. Due to the presence of lead it is either a blue-green, or blue and white striped color. The color pattern tends to be irregular even with the solid colour material. Amazonite can occur in different colours such as yellow, pink, red, and grey, however it is the blue green that is most popular and widely used.
Colors of Moonstone
Moonstones come in a variety of colors. The body color can range from colorless to gray, brown, yellow, green, or pink. The clarity ranges from transparent to translucent. The best moonstone has a blue sheen, perfect clarity, and a colorless body color. Another related feldspar variety is known as rainbow moonstone. In this variety, the sheen is a variety of rainbow hues, from pink to yellow, to peach, purple, and blue.
Moonstone Quality Factors
Color
The most highly favored moonstones should display: a colorless, semitransparent to nearly transparent appearance without visible inclusions, and a vivid blue adularescence, known in the trade as blue sheen. The finest moonstone is a gem of glassy purity with a mobile, electric blue shimmer.
Clarity
A good moonstone should be almost transparent and as free of inclusions as possible. Inclusions can potentially interfere with the adularescence.
Characteristic inclusions in moonstone include tiny tension cracks called centipedes. They are called this because they resemble those long, thin creatures with many legs.
Cut
Moonstone might be shaped into beads for strands, but by far the most common cutting style is the cabochon, a form that displays its phenomenal color or colors to best advantage. Moonstone cabochons are usually oval, but cutters sometimes offer cabochons in interesting shapes, such as the tapered sugarloaf—an angular cabochon with a square base.
Carat Weight
Moonstone comes in a wide range of sizes and carat weights. Fine-quality material is becoming scarcer in larger sizes.
Where is Moonstone found in the world?
Moonstone is found in Sri Lanka, Myanmar, Madagascar, Brazil, Australia and India. The various colors only come from India and the other sources yield white moonstone. In India, rainbow moonstone is mined in the southwest and blue is mined at Bihar in the center of the country.
What is Moonstone Value and it’s Price?
Moonstones are prized for their adularescence, an optical phenomenon that creates the appearance of billowy clouds of blue to white light with a moonlight sheen.
The more transparent and colorless the body and more blue the adularescence, the higher the moonstone value. Large quantities of near opaque material with various body colors, carved into simple “moon faces” and other figures, are available for pennies. Cabochons of translucent material, either white or with pleasing body color and adularescence, are fairly common on the market and command relatively modest prices.
Moonstone Price
It goes without saying that the clearer the stone, the more valuable it is. Prices for moonstones range from $10 to $1000, with clear moonstones free of inclusions such as centipedes or unappealing greenish tints commanding the highest prices.
Reference:
Moonstone (gemstone)
Moonstone Quality Factors
Moonstone Value, Price, and Jewelry Information
Moonstone
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