Tourmaline are precious stones, they are distinguished by a variety of color palette and amazing attractiveness of common varieties. Minerals are in the form of prismatic crystals. They are characterized by longitudinal hatching and a rounded triangular cross-section.
Tourmalines are distinguished by a rather high hardness of 7-7.5 on the Mohs scale and excellent gloss. These qualities contribute to the wide use of stones by jewelers. Minerals of bright saturated color and good purity, with a mass exceeding 10-15 carats, are rare. Such tourmalines belong to the highest price category. Designers of leading jewelry companies regularly use them to create their collections.
Tourmaline may have such optical effects:
The effect of "cat eyes" - due to the presence of thin channels filled with inclusions of gas-liquid consistency. It is found among tourmaline green color;
The presence of an "alexandrite" effect, which is a changeable color, depends on the presence of limited chromium. You can see the yellow-green light and the sun's rays and orange-red hues with artificial light turned on.
Tourmalines have a very complex chemical composition, due to the probability of replacing the atomic composition of the crystal lattice without disturbing its structural form. Gemologists have divided them into several groups that differ in chemical composition:
Sherly - ferrous minerals of black color;
Dravite - magnesian tourmaline brown, less green or black color;
Elbaites are stones that contain crystals of pink, yellow, green, or polychrome hues. Most tourmaline jewelry belongs to this group;
Uvita - similarity with the Dravites, in which there is a predominance of calcium over sodium. There are instances of green, brown, black;
Liddikoatity - similar to the Elbaites. The only difference is the higher calcium content, not sodium. They refer to a gemstone with a zonal pink and green color in the form of stripes;
Chromdaravites are dark green to black tones.
Participants in the market of precious stones practically do not use the names of these groups. Note that minerals and other mineral properties have tourmaline properties. The presence of iron or titanium is characteristic of blue, blue, green, yellow, orange, brown, brown crystals. Emerald green tonality depends on the presence of chromium or iron. In the minerals of pink and red colors there is an admixture of manganese.
On the jewelry market, it is customary to use the classification of tourmaline on the color palette:
Rubelite - tourmalines, have a pink or red color. Entry into the number of leaders in value in the jewelry market. The color range varies from light pink to deep pink, raspberry, aloy, violet and red tonality. Rubelite rich shades of red. The cost of individual copies may exceed $ 1,000 per 1 carat. Paraba, immediately after the neon blue tourmaline. An interesting fact is that the Japanese prefer high quality pink rubellites, and the red ones prefer the Chinese. Steady high demand for rubles in Asia, Europe and the USA is constantly increasing their value. The presence of a large number of included gas-liquid veils is characteristic of the rubellites. High purity specimens not included are rated very high.
Indigolite - tourmaline blue, greenish-blue, bluish-blue colors. They are quite a rare type of mineral. Stones of rich blue color are estimated as expensive as possible. Indigolites are shipped from Brazil, Afghanistan, Pakistan, Mozambique, Nigeria. The price of the best stones can exceed a thousand dollars per 1 carat.
Verdelite - a variety of tourmalines from dark green to light green, pastel "mint" colors. This is the most popular variety.
Chrome tourmalines - different bright green or rich green color. Chrome tourmalines are brighter than verdelitis and are valued several times higher.
Polychrome tourmalines - belong to an interesting group, which is characterized by the simultaneous presence of several colors. The most popular are the "watermelon" tourmaline, pink center and green edges.