This amazing gemstone processes two colors.
Preferred qualities show distinct pastel colors.
Bi-colored tourmaline is an amazing gemstone that shows two colors, such as pink and green or pink and blue, within a single crystal. There is mention of bi-colored tourmaline in books from the early twentieth century, but it was not until 1970s that this gemstone became commonly used in jewelry. It is now popular among jewelry designers, and one can come across adornments that fully bring out its charm.
A bi-colored tourmaline's beauty is judged by the balanced contrast between its pink and light green or light blue colors. Instead of colors that look as through a ruby and an emerald have been joined together, patterns of pastel pinks and greens (as shown to the next page) are preferred.
Tourmaline occurs in a wide range of hues. It is mined in all colors of the rainbow-red, orange, yellow, green, blue, and violet- but most of these are very dark. Bi-colored crystals having two separate colors, or material with three colors in a concentric ring-shaped pattern resembling the cross section of a watermelon, occur in limited quantities. Brazil, Mozambique, Nigeria, Siberia, and California in the United States each produce small amounts. Of these, Brazil appears to be the largest producer. Bi- or tri- colored tourmaline occurs because of differences in the crystal's chemical composition, caused by changes in the natural environment during formation. Ai different times during the tourmaline's formation, various color-causing elements such as iron, manganese, titanium, chromium, vanadium, and copper are incorporated into the crystal, causing layers of completely different colors to appear.
Bi-colored tourmaline is generally left untreated, subjected to no processing other than polishing. Since the gem is relatively high included, it develops fractures and breaks when heated. This gemstone should be treasured for the magnificent harmony of its two colors- a beauty that is created by chance within the earth- as well as for the knowledge that no two pieces are exactly alike.
Brooch, Platinum
Bi-colored Tourmaline 1pc
3.64ct
Untreated
Diamond 9pc
US $8,000
Name of Mineral : Tourmaline
Mohs Hardness :7~71/2
Refractive Index :1.624 x 1.644
Specific Gravity :3.06
Weight : 14.45 ct
Size (mm) : L 18.0 x W 10.7 x D 8.36
Untreated
Gem Quality
US $12,000
Weight : 69.0 g
Size (mm): L 48.1 x Diameter 25-28
untreated
US $1,500
Weight : 1.47 ct
Size (mm): L 10.0 x W 4.7 x D 3.49
untreated
US $300
Bi-Colored Tourmaline
Tourmaline often occurs as long crystals, and especially long crystals may be called "pencil" crystals. The most common type of bi-colored tourmaline is green at one end and pink at the other. Differences in transparency and coloration give each one a unique character.
Watermelon Tourmaline
As seen in the three watermelons slices to the right, each crystal has different patterns consisting of concentric areas of red, colorless, and green, or red, colorless, and blue. The watermelon tourmaline at the bottom shows three light red bands that intersect with a dark green border. There are beautiful designs created by nature.
BI-COLOR AND WATERMELON
Rough tourmalines that display more than one color in a single crystal either show a simple separation of color (as pictured below to the left), or they show different colors on the inner and outer portions (as shown below to the right). Stones such as the ones on the left are typically polished into bi-colored tourmaline. The rough on the lower right is often sliced and made into gemstones called "watermelon" tourmalines.
Weight : 8.42 ct
Size (mm): L 22.8 x Diameter 5.8-6.3
untreated
US $600
Weight : 4.30 ct
Size (mm): L 15.1 x Diameter5.1-5.9
untreated
US $400
Weight : 2.51 ct
Size (mm): L 12.9 x W 5.4 x D 3.89
untreated
US $500
JUDGING QUALITY
Because of the unlimited variety in the combinations of colors and shapes of bi-colored tourmalines, there is also wide latitude in judging their quality, based on personal preference. It is important to first confirm that the gemstone's beauty is well balanced by looking at its overall appearance.
Next, even if the individual colors are somewhat light, confirm that the gem has a relatively high transparency and that there is a distinct separation between the colors. The stone's quality is judged as poor if it is cloudy or has large defects, if its balance is thrown off by one color being too strong or too weak, or if the two colors are not distinct.
HOW TO CHOOSE
When choosing a stone for jewelry use, the key is to select one that shows a distinct separation of pink and light green or light blue pastel colors, without any noticeable defects that detract from beauty.
Since many tourmaline crystals have a long shape, polished stones are often long as well. A piece of unique and exhilarating jewelry based on a solid design concept leaves us with an appreciation of how human imagination can capture the beauty nature has bestowed upon us.
The value of a three-carat-size bi-colored tourmaline of jewelry quality is approximately US $600 for the stone alone.
(2001)
QUALITY SCALE
BI-COLORED TOURMALINE
Untreated
A GEM OF VALUE
Weight:3.64ct
Size(mm):L 14.8 x W 6.2 x D 4.20
Untreated
Gem Quality
US $1,500
The 3 quality zones as they appear in the quality scale
Quantity distribution of gems that are polished to 3-carat size
