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Buyer’s guide: moonstone (Adular)

Buyer’s guide: moonstone (Adular)

Buyer’s guide

June 25, 2021

moonstone (Adular)
moonstone (Adular)

On the photo: moonstones from the Gem Lovers collection

Natural moonstone is an adular variety from feldspar mineral group. It’s an interesting gem that deserves special attention. Among the material that is marketed under the name “moonstone” only a small percentage is truly natural quality rare stone. The universal favorite adular won hearts not by bright color and excellent play, but by a modest bluish radiance reminiscent of the light of the Moon and delicate milky translucency. In this article we will reveal the nuances of choosing a moonstone, talk about its nature of color, clarity, processing, deposits, and how to find out if a real stone or fake. In conclusion we also present the current market prices for adulars. Article navigation:

Colors and types of moonstone

Under the name “moonstone” there are on the market a few of feldspar family minerals: orthoclase and plagioclase, including varieties of albite, oligoclase and labrador.

The color of the moonstone consists of two components:

  • Mineral’s own color
  • Optical effect (irisation or adularescence, cat’s eye)

Moonstones come in different colors: white, gray, brown, peach, orange, cream, dark, black, greenish, yellowish. The adularescence as a rule has a blue color may look like a bright highlight on the surface of the cabochon (silver, pearl irisation) or like a rainbow (labradorescence). Sometimes there are samples with the effect of a cat’s eye and asterism in the form of a 4-ray star.

In this article we will consider the most valuable species – adular (white translucent with light blue irisation) and rainbow moonstone.

The classic adular moonstone is a noble translucent mineral orthoclase with blue or milky white irisation.

The rainbow moonstone refers to plagioclase in composition. It is transparent to a translucent gem with rainbow tints in the entire volume of the cabochon.

When choosing a moonstone pay attention to adularescence (area, intensity, color) – the main evaluation criteria for this gemstone. The more visible and colorful the effect than the higher the value. Optical effects best reveal their beauty under a point source of light (sun, lamp) against a dark background. With diffuse daylight the effect is almost not manifested.

Clarity

This is the case when the public treats mild imperfections condescendingly and even respectfully. Here the main thing is not to get confused in the concepts of transparency and clarity. Transparency characterizes the degree to which a stone transmits light, and clarity – the presence or absence of defects and heterogeneities. Moonstone can be transparent and have a low clarity, for example, contain cracks. Or maybe translucent, but with high clarity. There are also transparent and clean adulars, but, as a rule, in such stones the effect of blue irisation is weakly expressed. Well, there is no perfection in the world…

The main part of moonstones on the market is characterized by a large number of internal defects and heterogeneities that affect beauty and durability, such samples only slightly shine through, looking almost opaque. Inclusions, cracks, developed cleavage planes can occupy the entire volume of the stone. All the more valuable and less often really clean translucent and transparent samples.

high and low clarity adular cabochons

In the photo: high and low clarity adular cabochons

Eye clean stones (without inclusions and cracks visible to the eye) are considered the most valuable. They are mined extremely rarely. For individual jewelry minor inhomogeneities are allowed in the form of a clouds, small inclusions throughout the volume. It doesn’t worsen their appearance at all, but it adds personality.

Cut

Cabochon is the most popular form for adular. It is in the cabochon that the moonstone reveals the most spectacular beauty of irisation. The bottom of the cabochon can be flat or slightly convex. The classic forms of adular cabochons are an oval and a round; cushion, pear and marquise are less common.

It is extremely rare to meet faceted adular on the market. Usually it’s a single collection samples, which is caused by the complexity of the faceting of the mineral and the fact that irisation is much more modest.

It is important to correctly orient the crystal during processing so that the irisation is located exactly in the center of the cabochon. The cost is affected by the quality of processing; pay attention to this. And here 2 factors are important: cabochon geometry and polishing. Due to the difference in hardness in different directions of the crystals, the cabochons of the moonstone often acquire an asymmetric shape; therefore, cabochons with a flattened top or an elongated oval shape, close to a rectangular cushion, can often be found on the market. Polishing adulars is a technically difficult task, therefore, a lot of stones on the market are of average quality, when viewed through a loupe on the surface of the cabochon, scratches, scuffs, and unpolished areas can be seen. High-quality polishing gives a specular highlight on the surface and immediately improves the overall perception of the stone.

Treatment

Moonstone is rarely treated. Oiling sometimes results in improved clarity and overall appearance in fissured specimens.

Weight

Large finds of good quality crystals are very rare if we talk about transparent gem adulars.

Small pieces of raw materials are used to make cabochons. Blue moonstones look spectacular even with a diameter of 2-6 mm. The price per carat of such stones is not high.

With a weight of 5 carats, a clean adular with a blue shine as a central stone becomes interesting for making individual jewelry. Large clean cabochons with a weight of 15-20 carats and more are much higher. Samples of blue moonstones more than 40 carats are unique collector level finds that are individually evaluated.

Geographical origin

Deposits of different types of moonstones are found in many countries including Russia (in the Urals and Karelia).

As for valuable varieties like adular and rainbow variety only a few places on the planet can be distinguished:

  • Sri Lanka
  • Tanzania
  • India
  • Madagascar
  • Burma

Ceylon and Tanzanian moonstones are considered among the best.

How to distinguish a real moonstone from a fake?

Moonstone is very popular. You can find it in beads, jewelry, pendants, key chains, inexpensive rings and silver earrings, but mainly opal glass imitation is sold under the commercial name moonstone. It is really very clean, translucent, has a bluish tint and is cheap. But, unfortunately, it has nothing to do with natural gem adular.

How to understand that it is a fake opal glass? Distinguishing imitation from the original is not difficult. The easiest test is to look at the specimen in the light and under the incident light. Glass in transmitted light will be yellow or orange and under incident light – milky-bluish. Also glass imitation of a moonstone often contains inclusions in the form of bubbles eye clean, as well as stains – stitches. The real moonstone looks very different, it will not change in the lumen, but the effect of irisation appears only with incident light and is most visible with a point source of light.

If you have doubts about the natural origin of the specimen take it to the gemologist for examination or contact the gemological laboratory for certification.

On the video: natural moonstone cabochons

Price of good quality moonstones

To answer the question “how much does a carat of a real moonstone cost”, we consider a variety of adular of the following characteristics: white, translucent, inclusions or cracks that are hardly noticeable to the eye, medium-intensity bluish irisation, oval cabochon shape with good geometry and acceptable polishing.

  • 5 ct – 40-60 USD/ct
  • 10 ct – 60-80 USD/ct
  • 15 ct – from 100 USD/ct

Large specimens are evaluated individually depending on the characteristics. The cost of a large blue adular can reach several hundred dollars per carat with a bright neon adularescence.

Rainbow moonstones are rated much higher due to their rarity. To get an individual consultation and find out the price of copies of specific characteristics, please contact us.

In the Gem Lovers catalog you can choose and buy natural moonstone.

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