Spinel has long been confused with ruby, but its
high hardness and excellent durability make it a gemstone to be treasured.
Many spinel crystals have an octahedral shape, just like diamond rough. The name "spinel" is derived from the resemblance of these crystals to thorns (spina in Latin).
It wasn't until 1783 that red spinel and ruby were recognized as different minerals. The "Black Prince's Ruby" set in the center of the British Imperial State Crown is actually not a ruby, but a red spinel. Acquired by Edward, Prince of Wales (the "Black Prince") during the 14th century, this lovely spinel remains the main stone of the Imperial Crown to this day.
In precious Stones (1896), the German mineralogist Max Bauer reported that spinals are "far more free from faults" than rubies, and that a one-carat spinel is worth "about half as much as ruby of equal weight," or "£5 to £7 10s."
The beauty of red spinel lies in its pure red color. Because spinel is a singly refractive mineral, it does not exhibit pleochroism. The spinel on the next page (from Mogok, Myanmar), with its mosaic of light orangey-red and dark red created by its faceted cut, exhibits a balanced beauty. This spinel is a "cushion" shape (a rectangle with rounded corners); the ancient method of fashioning spinels was simply to polish the stone's surface, resulting in finished gems that closely followed the shape of the rough material, much like today's cabochon cuts. The beauty of a cabochon-cut gemstone emphasizes the fineness of the stone's color, but in the faceted styles that currently predominate, the key point is the three-dimensional beauty created by the mosaic pattern. Spinels are not heat-treated.
Spinels are especially attractive in reddish colors, and they alsopossess high hardness and durability. So why aren't spinels as well known as rubies? The main reason is a lack of sufficient quantities for successful marketing, due to limited mining production.
Ring, Gold/Platinum
Spinel 1pc
0.76 ct
Untreated
Diamond 10 pc
US $5,000
Name of mineral : Spinel
Mohs hardness : 8
Refractive index : 1.718
Specific gravity : 3.60
Weight : 2.03 ct
Size (mm) : L 7.5 x W 6.1 x D 5.42
Untreated
Gem quality
SOURCE OF SPINEL
The current main sources of spinel are Myanmar, Sri Lanka, and Tanzania. Mining also takes place in Afghanistan, Thailand, and Russia. Most spinels are mined from alluvial deposits, where rough crystals that were transported by ancient rivers accumulated along with dirt and gravel.
Weight : 0.73 ct
Size (mm): L 7.4 x W 4.8 x D 2.79
untreated
US $400
Tanzania
The Tunduru mines, located approximately 400 kilometers (240 miles) south of Dar-es-Salaam, have been operating since late 1994. Tundurn is an area of alluvial deposits spanning 40 kilometers (24 miles), said to be worked by some 4,000 miners. Red spinel is mined here, along with diamond, sapphire, alexandrite, cat's eye chrysoberyl, tsavorite, and tourmaline. Most of the spinel is accessory-quality material falling within tone levels 2 and 1 and beauty grades A through D on the quality scale. However, some bright pink material like the one shown in the photograph is also mined.
Sri Lanka
Blue, violet, and black spinels are mined in the Ratnapura area of southwest Sri Lanka, but red spinel production is rare. The surfaces of the rough gemstones found here are weathered and worn.
Weight : 1.07 ct
Size (mm): L 7.1 x W 5.2 x D 3.70
untreated
US $200
Weight : 0.88 ct
Size (mm): L 7.0 x W 5.1 x D 3.17
untreated
US $100
Myanmar
The Mogok region of Myanmar is famous for its rubies and sapphires, but it is also a source of orange, green, blue, and violet spinels. In addition, limited qualities of fine-quality red and pink spinels are mined here. Rough crystals with weatherworn surfaces are found here also, as well as perfectly formed octahedral crystals.
JUDGING QUALITY
When judging the quality of red spinel, the darker colors seen in stones from Mogok and lighter colors of Tanzanian material are considered separately. Darker spinels typically resemble rubies, but when compared side-by side, the difference between the purplish red of ruby and the crimson red of spinel becomes obvious. Spinels will look slightly orange to the eye that is accustomed to the purple-red of rubies.
Red spinel that exhibits the beauty of a crimson-red mosaic pattern is considered gem quality. Some lighter red spinels are highly transparent, giving them a clear and pleasing quality. These are classified as jewelry quality because of their light tone, but some of them possess a beauty that surpasses gem quality and deserve very much to be used in jewelry.
HOW TO CHOOSE
The main consideration in choosing a red spinel is finding a color that is close to pure red. A highly saturated red, even if somewhat light, is an appealing color. Look for beautiful color first, instead of insisting on a dark red color just because it is a red spinel. Since mining qualities are essentially limited, it is important to search patiently and select a pleasing pink or red spinel with no violet or brown tint.
Next, consider the quality of the stone's overall appearance. As long as the stone is not excessively deep, or does not shown a window (an area of washed-out color seen when the stone is viewed from above), a certain degree of compromise is necessary. The beauty of the color's hue is by far the most important point when choosing a red spinel.
The value of a three-carat-size red spinel of jewelry quality is approximately US $6,000 for the stone alone.
(2001)
QUALITY SCALE
RED SPINEL
Untreated
A GEM OF VALUE
Weight:0.70ct
Size(mm):L6.6 x W4.9 x D2.77
Untreated
Jewelry Quality
US $600
The 3 quality zones as they appear in the quality scale
Quantity distribution of gems that are polished to 3-carat size
