This article appeared in the Mouawad Group magazine, Monemtum International, volume 5, no. 18
September-December 1998, pp 22-25
Reproduced with kind permission of Mouawad

Properties of high quality Demantoid Garnets

Generally speaking, and in comparison to rubies, sapphires, diamonds and emeralds, garnets are considered a relatively inexpensive gemstone. Garnets occur, however, in a series different color varieties, ranging from green to orange, and red to purple, with the exception of shades of blue. The prices of garnets vary accordingly. Several major factors can cause a dramatic increase in the price of garnets: the stones’ color, size, brilliance and rarity. Whereas orange (spessartine, Malaya), red (almandine, rhodolite), purple (Pyrope), and pastel (grossular) garnets are relatively inexpensive, if not excessive in size and transparency, green garnets (Tsavorite and Demantoid) are considered the most valuable. The top of the beauty and rarity scale is marked by the over 3 to 5 carat faceted Demantoid garnets of intense emerald-green color.

Demantoid crystals are chemically composed of the elements Calcium, Iron, Silica and Oxygen. These are not rare elements. Demantoid garnets contain traces of Chromium without which the garnets would be Andradite, found abundantly all over the world. The rarity of these demantoid crystals is due to extremely complicated geological coincidences, which are necessary for their formation. Such circumstances are extremely rare, gem qualities are only found in a few places on earth, most notably in the Ural Mountains of Russia.

The most beautifully colored demantoids are considered the highly saturated greens, matching the color of the finest Colombia emeralds, while greens with a yellow or brown overtone are less highly prices on the market today.

The highest prices for demantoid garnets upwards of US$ 20,000 per carats for stones over 5 carats. The largest sizes generally do not exceed 10-20 carats. In comparison, such prices are normally only encountered for highest quality sapphires.

One of the major reasons that the demantoid garnets holds a special niche in the world of gemstones is its unique beauty, namely the fact that it combines some of the properties of diamonds as well as those if emeralds. Demantoids have a brilliance similar to that of diamonds, due to their high refractive index. Like diamonds, demantoids have only once color if viewed in different crystallographic directions. By comparison, emerald have over-tones of yellow or blue if viewed from different crystallographic directions, because of their so-called dichroism. Demantoids are softer and therefore less durable than diamonds.

However, they are also less brittle than emeralds, and the oiling of demantoids is not feasible because of their high refractive index relative to the liquids used for such enhancement.

The demantoid is faceted in the same way as a diamond, in brilliant cuts of round. Oval, cushion and pear shapes. The emerald cut is not used. The face-up appearance- fire and brilliance so resembles diamonds that the name, which means “diamond like” was promptly given when demantoids were discovered in the Ural Mountains over one hundred years ago.