Tourmaline

Tourmaline gemstone

The name "tourmaline" comes from the Sinhalese word "turamali," which means "mixed colored stones". Tourmaline is known for their variety of color palettes and the amazing attractiveness of the varieties that exist.

The gems are shaped like prismatic crystals. They are characterized by a longitudinal stroke and a rounded triangular cross-section.

History

Tourmaline has been used for a variety of purposes throughout history. In ancient Egypt, tourmaline was used to make scarabs, small beetle-shaped amulets that were believed to bring good luck.

The first specimens of tourmalines were brought to Europe from Ceylon (Sri Lanka) at the beginning of the 18th century. Europeans owe their acquaintance with these wonderful stones to the Dutch sailors. Interestingly, the sailors used tourmalines for cleaning their smoking pipes. As it turns out, the heating causes the stones electrification and they attract ash, which cleans the pipes. The wide variety of colors of tourmalines led to the fact that they were often confused with other minerals of similar coloring. Pink-red tourmalines became popular in Europe and Russia in the mid-18th century. The wonderful jewelry and decorative objects created by the jeweler Carl Faberge contributed greatly to its popularity.

Uses

Today, tourmaline is still used in jewelry, but it also has a number of industrial uses. Tourmaline is a piezoelectric mineral, which means that it generates an electric charge when it is subjected to mechanical stress. This property has been used to create pressure sensors and other electronic devices. Tourmaline is also used as a gemstone in jewelry and other decorative items. Designers from the leading jewelry companies regularly use them in their collections.

Tourmaline jewelry became fashionable in the XVIII century. These stones were repeatedly confused with other gems and used to decorate the crowns of kings and emperors. Modern jewelry brands regularly release collections with tourmalines. But the jewelry pieces with these beautiful stones are very rarely seen in the showcases of Russian jewelry stores. The thing is that tourmalines are quite rare as compared to amethysts, citrines, or blue topaz. Almost all jewelry pieces with tourmalines are exclusive. Most often, there are different models of earrings and rings decorated with tourmalines, but jewelry sets are seldom sold. All kinds of jewelry pieces made by the well-known brands of Tiffany & Co, Van Cleef & Arpels, Chopard, and Bulgari are extremely popular

Properties

Physical properties

Tourmalines have a rather high hardness of 7-7,5 on the Mohs scale.

Chemical properties

Tourmalines have a very complex chemical composition, due to the possibility of substitution of the atomic structure of the crystal lattice without disturbances of its structural form. Experts gemologists made a division of the family of tourmalines into several groups differing in chemical composition:

• Sherls are ferrous minerals of black color;
• Dravites are magnesian tourmalines of brown, less often green or black color;
• Elbaite: stones that contain an admixture of sodium and lithium, which gives the crystals pink, yellow, green, or polychrome hues. Most of the jewelry tourmalines belong to this group;
• Uvites are similar to dravites, with a predominance of calcium over sodium. Some occur in green, brown, and black;
• Liddicoatites - similar to elbaite. The only difference is the greater content of calcium, not sodium. They are referred to as gemstones with zone pink and green coloring in the form of bands;
• Chromodaravites, which are characterized by a color range from dark green to black.

Optical effects

• The "cat's eye" effect is due to the presence of thin channels filled with inclusions of gas and liquid consistency. Occurs among green-colored tourmalines;
• The "alexandrite" effect, which is a change of colors when the light
  source changes, depends on the presence of chromium impurities. The yellow-green coloring of tourmaline may be observed under the rays of sunlight and orange-red hues when the artificial light is switched on.

Participants of the market of precious gems is almost not used the names of these groups. Note that the color and some other physical properties of tourmalines depend on the chemical composition of minerals. The presence of iron ions or titanium characteristic blue, blue, green, yellow, orange, brown, brown crystals. Emerald green tone depends on the presence of chromium ions or iron. In minerals pink and red color is present, the admixture of manganese.

Color palette and price

• Rubellite – is a tourmaline with a pink or red color. They are among the leaders in the growth of value on the jewelry market. The color range varies from pale pink to deep pink, crimson, scarlet, purple, and red. Rubellite with rich red hues belongs to the highest price category. The price of some samples can go over $1,000 per carat. This makes rubellite the second most expensive variety of tourmaline, right after the neon-blue tourmaline Paraiba.
• Indigolite – are blue, greenish-blue, and bluish-blue tourmaline. They are a fairly rare variety of the mineral. Stones of rich blue color are valued at the highest price. The price of the best stones can exceed one thousand dollars per carat.
• Verdelite – is a variety of tourmalines that vary from dark green to light green, in pastel "mint" colors. Verdelites are usually of high purity and are the most popular variety. The cost of such tourmalines of high quality jewellery ranges from $300-700 per carat.
• Chrome Tourmaline are either bright green or deep green, depending on the amount of chromium they contain. Chrome Tourmaline are much brighter than verdelites, and are valued several times over. 
• Polychrome tourmalines belong to an interesting group characterized by the simultaneous presence of several colors. Large and clean specimens with a beautiful color change on the average on the world stone market worth $100-400 per carat.
• Paraiba is the most expensive tourmaline. The cost of the Paraiba, depending on the purity and color saturation is in the range of $1500-30000 per carat. In recent years the price for Paraiba tourmalines on the market is growing rapidly, sometimes 20-30% a year.
• Watermelon tourmaline is a type of tourmaline gemstone that is named after its distinctive color pattern, which resembles the skin of a watermelon. It is a bi-colored stone that displays shades of green and pink or red, often with white stripes in between the two colors. This gemstone is prized for its unique beauty and is commonly used in jewelry making.

Tourmalines buyers guide

The four C's are the accepted standard for judging the quality and value of diamonds. This method is also used to evaluate gemstones:

1. Carat: The weight of the stone, measured in carats, which determines the size of the stone.
2. Cut: The cut of the stone, which affects its sparkle and overall appearance.
3. Color: The hue, tone, and saturation of the stone, which are the key factors that determine its beauty.
4. Clarity: The absence or presence of inclusions, blemishes, and other imperfections within the stone, which affect its transparency and overall appearance.

Treatment

Specialists do not synthesize tourmalines. Various methods of treatment are used to enhance the quality of the coloring of stones. Thermal treatment is used to brighten tourmalines with dark green or blue-green coloring. If the pinkish-red tourmalines are heated strongly, they discolor completely. Because of this, the darker stones go through a low-temperature heat treatment. The temperature treatment removes the entire gamut of unnecessary pink-purple tonality in the Paraiba tourmalines, leaving beautiful blue and greenish-blue tones.

The irradiation technique is necessary when improving the color saturation of pink-tinted tourmalines. In addition, irradiation of colorless stones gives them a pink hue, and irradiation of light yellow tourmalines adds to their brightness. Specialists use the technology of filling cracks with polymer to visually improve the clarity of the stones. Paraiba tourmalines with a significant number of cracks are treated with this technology after heat treatment. Discoloration of channels in the stones is performed by acid etching. A diagnostic report from the laboratory is necessary when purchasing tourmalines, especially expensive Paraiba, because the fact of clearing significantly affects the cost of stones.

Origin

Most of the high-quality stones for the jewelers come from Brazil. In addition, there are supplies from Mozambique, Madagascar, Nigeria, Afghanistan, Tajikistan and Pakistan. Russian tourmalines are mined in the Urals.