da sapere — 三月 6, 2019 at 4:30 上午

Everything about tourmaline

Often confused with other stones, tourmaline is characterized by a wide range of hues and shades. No coincidence that the name comes from a Sinhalese word turmali, used to indicate carnelian and stones of different colors from Sri Lanka. The main varieties of tourmaline used in jewelry is one that defines the classification of the mineral as Elbaite, which is also a synonym for green tourmalines. Much used Rubellite also, which color are from red to pink, and the rare Indicolite, from a deep blue and exceptional luster.

Features Tourmaline is a dichroic stone: each crystal, usually very long, has two colors (one dark and one light), that change as intensity depending on the angle of observation.

Color There are many and with different shades. The most sought stones are the Paraiba tourmalines, homonymous field in Brazil, although the name is used for gems from different backgrounds such as Mozambique and Nigeria, when they have this range of shades: Caribbean blue, peacock blue, neon blue, copper green, neon aquamarine, azure, turquoise generated by the traces of chromium. A trace element, chromium, which gives its name to a deep green stones that are found in Tanzania, although the color in this case is given by the presence of vanadium. A great blue saturation, brightness and purity is the rare tourmaline Indicolite. There are, then, the Rubellite with its shades ranging from pink to vivid red, tourmaline Watermelon or watermelon, true wonder of nature, because two-tone: the center is red, surrounded by an outer layer of green, or vice versa.

Source The most important deposits are in Afghanistan, Pakistan, Russia, Burma, Sri Lanka, and United States (California and Maine). Many African countries have recently become major producers of tourmaline, particularly Madagascar, Namibia, Mozambique, Tanzania, Nigeria and Malawi.

Evaluation is not a simple thing due the amount of varieties and colors. The first thing to do is to examine the stone in sunlight: a green gem under an incandescent bulb may appear almost black, while a pink or red appears gray or brown. If, even under artificial light, keeps its natural tones, is likely to be a stone with a fine color. But beware, the primary color should be predominant for 70-75%. The rest of percentage is obviously a hue, ie a secondary color which, however, may change depending on the illumination, natural or artificial. Moreover, there is no general rule on dimensions and prices: some tourmalines are found only in small sizes and are used as beads in a very low cost, while others are more available in 10 or more carats. The evaluation also takes account of its clarity, which has three degrees defined by the Gia (Gemological Institute of America, the most famous center of research and teaching mineralogy of the United States): if the green tourmaline is usually classified type I, that means, has a slight inclusion visible to the naked eye, blue, orange, yellow, multi-color (except watermelon varieties) and some pink specimens stones have minor inclusions and are grade II, while the red ones , pink and watermelon belong to the third category III where noticeable inclusions are expect ed as it appears from the photos below. Tourmaline is normally not subjected to heat treatment and if this happens does not affect its value.

Cartier, spilla Caresse d'Orchidées, con una rubellite centrale, taglio cabochon
Cartier, spilla Caresse d’Orchidées, con una rubellite centrale, taglio cabochon
Pomellato, anello Pom Pom con tormaline verde foresta, verde menta e diamanti
Pomellato, anello Pom Pom con tormaline verde foresta, verde menta e diamanti
Chopard, anello Red Carpet 2013 con tormalina turchese Paraiba
Chopard, anello Red Carpet 2013 con tormalina Paraiba
Harry Winston, anello pezzo unico con tormalina Paraiba taglio cabochon e diamanti
Harry Winston, anello pezzo unico con tormalina Paraiba taglio cabochon e diamanti
Tormalina Elbaite proveniente dalla miniera Cruziero di Santa Maria do Suaçuí, nella regione Minas Gerais in Brasile
Tormalina Elbaite proveniente dalla miniera Cruziero di Santa Maria do Suaçuí, nella regione Minas Gerais in Brasile
Van Cleef & Arpels, anello Pierres de Caractère Lotus d'Orient in oro bianco, tormalina ovale del Mozambico tipo Paraiba di 24.44 carati, diamanti taglio brillante e a pera, zaffiri tondi e chrysoprase scanalati
Van Cleef & Arpels, anello Pierres de Caractère Lotus d’Orient in oro bianco, tormalina ovale del Mozambico tipo Paraiba di 24.44 carati, diamanti taglio brillante e a pera, zaffiri tondi e chrysoprase scanalati
Rebecca Dana, orecchini con tormalina anguria, tormaline rosa e diamanti
Rebecca Dana, orecchini con tormalina anguria, tormaline rosa e diamanti
Boucheron, spilla Fleur De Jour in oro bianco con tormalina rosa, cristallo di rocca, diamanti bianchi, e madreperla grigia
Boucheron, spilla Fleur De Jour in oro bianco con tormalina rosa, cristallo di rocca, diamanti bianchi, e madreperla grigia
Piaget Couture Précieuse, anello Magnificent Adornments Inspiration in oro bianco con rubellite e diamanti
Piaget Couture Précieuse, anello Magnificent Adornments Inspiration in oro bianco con rubellite e diamanti
De Grisogono, anello cocktail con Rubellite taglio cabochon
De Grisogono, anello cocktail con Rubellite taglio cabochon

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