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Russian Gemstones Encyclopedia

Vladimir Bukanov. Russian Gemstones Encyclopedia

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

RUTILE, GROUP: RUTILE, ANATASE, BROOKITE


RUTILE group (Rutil—Rutile—–утил) (Werner, A.G. 1803), from Lat. “rutilus” – golden red, alluding to its common color, especially in transmitted light. In the nature titanium dioxide is represented also with polymorph modifications of rutile – anatase and brookite, which are described lower.

Composition & Properties. Rutile oxide – TiO2, tetragonal system. Hardness 6-6.5. Density 4.2-4.3. Diamond luster to half-metallic one. Cleavage in one direction. Fragile. Rutile is usually represented with long-columnar to needle crystals or their regular clusters in the form of sagenite grates and star aggregates. Sometimes it forms solid grained masses. Transparent to non-transparent. Color: red, reddish-brown, bluish and violet, greenish because of the admixture of niobium and bright green because of the admixture of chromium, in hair-shaped aggregates it is yellow or gray. Such aggregates can be observed as inclusions in albite, adularia, rock crystal, garnet and apatite. In agate they observed sagenite grates – sagenitic agate. The most often and beautiful case of inclusions of rutile is quartz hair stone or rutile quartz. Parallel-oriented inclusions of fine-needle aggregates of rutile produce the effect of silky in ruby and sapphire. In star ruby, star sapphire and rose quartz they observe asterism because of inclusions of needle rutile. When rutile replaces plates of hematite and ilmenite, rutile is formed on their surface, which is an example of pseudoasterism. As a variety of rutile they classify black ferrous rutile, or nigrin and resembling it but separate minerals ilmenorutile.

Deposits. Rutile is formed at deposits of different types, mainly in the process of metamorphism. It is well preserved at placers. In Russia, rutile was discovered at first in the Urals in 1770; it was called by P.S. Pallas – radiant schorl. Then, it was described by Hermann as black schorl – in the Middle and South Urals in 1789, including the material from the Altyanskaya placer near Miass. At placers of the Middle Urals, they find gravel crystals of gem-quality rutile up to 35x7 cm. in size and up to 125 gm. in mass. In pegmatites of Izumrudnye Kopi (Emerald Mines), cherry-red and black crystals of rutile reached 10 cm. long. In the South Urals, crystals of blood-red rutile, available for faceting, were found in quartz veins. In the Slyudorudnik, in the region of Kyshtym, they reached 25 cm. long, and some crystals were up to 1 m. Large isolations of violet rutile were discovered not rarely in eclogites, where its crystals were 20-30 cm. long and 8 cm. in cross-section, with the weight up to 5 kg. At the rock crystal deposits of the South Urals Astaf’evskoye, Terensay and Rechnoye (Dzhaman-Akzhar) there were findings of crystals of rock crystal with inclusions of needle rutile. Similar quartz hair stone are widespread in the Subpolar Urals Mts. in alpine veins, too. The most beautiful quartz hair stone with rutile are found at the deposits of rock crystal Dodo, Parnuk, Puiva, Skalistoe, Feiko-Shor, Central Lapcha, Choln-Iz and others. In one of veins of the Puiva deposit they found plate crystals of orange rutile up to 100x6x1 mm. In the basin of the Kozhim River, on its tributary the Balban Yu River, unusual concentration of inclusions of rutile in quartz was observed in one of rock crystal veins of the Pelingichey-3 deposit. There columnar veined quartz was so heavy enriched with small needles of rutile, that it was red-brownish in color. The thickness of the zone of such rutilization in selvage of a rock crystal pocket reached 0.5 m. It is a perfect rough material for cut in cabochon and tumbling. In Azerbaijan, in the Zangezur Ridge, in the region of the Paragachay deposit, in the Kapydzhik Mt., they discovered crystals of rutile up to 7 cm. long. In Tadzhikistan, at the Kukurt deposit of scapolite, in amphibole-scapolite veins, they found clusters of rutile up to 20 cm. in size, with segments, available for faceting. In alpine veins of deposits of Switzerland, Austria and Italy findings of quartz hair stone with rutile are well-known. In France, at the La Villeder deposit, Morbihan Dept., Brittany, up to 5 cm. crystals of rutile; also in Italy near Trentino-Alto Adige, were found. On Madagascar, crystals of rutile up to 15 cm. long were found at the Mananara deposit. In South Australia, findings of rutile are typical for rock crystals deposits in the region of Adelaide.

However, the best material of such type and in the largest volumes is extracted in Brazil, from deposits of the states of Bahia and Minas Gerais. In Bahia State, at the Novo Horizonti (form. Ibitiara) deposit the size of crystals of rutile, which are represented as inclusions in quartz, reaches 12 cm. At diamond fields, rutile is found in the form of paredrite and gravel pebbles, which have the local name titan-favas. In the U.S.A., crystals of rutile up to 25 cm., available for processing, were found in Georgia, at the Graves Mt. deposit, Lincoln Co.; and in North Carolina – up to 7 cm., at the Stony Point deposit. In Canada, gem-quality rutile was extracted at the deposits St Urban de Chalevu and St Paul Bay, Québec Prov. In Mexico, similar rutile was extracted as additional material from ore at the Guadelupe de Tissour mine, Oaxaka State.

Synonyms. Cajuelite, obs. | Dicksbergite, after the discovery location near Dicksberg, Sweden | Favas, from Port. “kidney bean”, after the shape of pebbles at placers. Also name are pebbles anatase, tourmaline, chrysoberyl and kyanite in the Brazilian diamond gravel deposit | d’Amour flèche, Fr. | Venus hairs | Schorl-like garnet | Titanic ore | Paraedrite (paredrite), from Gk. “paredros” – an assistant | Red schorl | Titan schorl | Money stone, local name in the U.S.A. | Titanschorl.

Cut Gems. Faceted stones up to 3 ct. display beautiful play of color, because of the index of refraction and dispersion more high, than that one of diamond. Such stone, 3.7 ct. in mass, is kept in the Museum of Calgary, Canada. Black variety of rutile – nigrin when faceted resembles black diamond in luster. Popular among jewelers rutile hair stone were in fashion in the 18th cent. They were cut in cabochons and flat insets for brooches and other jewelry work of art. Brownish crystals of rutile can be improved with annealing to 1000°C in oxidizing environment. After it brownish color transforms into lemon-yellow one.

Synthesis. One of the first successful imitations of diamond was synthetic rutile, received in the U.S.A. in 1948 with the method of Verneiile – in crystals up to 10 ct. Stones faceted from them were called Titania brilliants. In the U.S.A., also the method of growing of synthetic rutile with asterism was patented. Adding different admixtures to the composition of rutile provides a wide scale of colors: from red to dark red, from reddish-amber to yellow, from light blue to dark blue and blue-black. Only the list of synonyms of the trade name synthetic rutile proves its popularity. Nowadays, synthetic rutile, as an imitation of brilliant, let the way completely to cubic zirconia (phianite).

Synonyms. Synthetic rutile – Astryl | Brilliante | Rainbow diamond | Magic rainbow diamond | Diamonist | Diamonite | Capra gem | Gava gem | Jarra gem | Java gem | Johannes gem | Kenya gem | Kima gem | Kimberlite | Kimberlite gem | Rainbow gem | Tirum gem | Titan gem | Zaba gem | Lusterite | Miridis | Titanium rutile | Titania stone | Midnight Titania stone | Tania-59 | Star tania | Titania | Sapphirsied titania, and other.

Similar gemstones. Rutile looks like cassiterite, tourmaline and zircon.

Anatase (Anatas—Anatase—јнатаз) (de Lisle, 1783, Haüy, R.-J. 1801), from Gk. “anatasis” – extension, is alluding to the greater length of the common pyramid as compared to other tetragonal minerals. Oxide – TiO2, tetragonal system. Hardness 5.5-6. Density 3.6-3.9. Diamond luster. Perfect cleavage in two directions. Fragile. It is found mainly in the form of bipyramidal crystals, but rarely in table shapes, too. Color: black-blue, greenish-yellow, brown, honey-yellow. Anatase is a typical mineral of alpine veins. In Russia, its findings are not rare at rock crystal deposits of the Urals. The size of its crystals is usually not more than 2 cm. long there. Anatase is also well known in the Middle and South Urals, where its large crystals were found at placers. A new type of deposits of anatase is metasomatic of the Murun alkali massif in Yakutia, where the size of crystals of anatase reaches 2 cm. In the Khabarovsk Region, at the Udacha deposit, 60 km. to the south from the massif Kondior, they discovered crystals of anatase up to 3 cm. In Switzerland, in alpine veins of the deposits St Gottard and Binntal (Binn Valley), they found crystals of anatase up to 5 cm. in size, including those of yellow wiserine. In France, in alpine veins of the deposits Bourg d’Oisans, Iséré Dépt., and in La Landazerie, Loiret, crystals of anatase were of the same size. In Norway, it was discovered at the Tusse deposit, in the region of Hardangervidda, in crystals up to 3 cm. In the south-western part of Poland, near Elenja Góra, in granite quarries findings of black anatase up to 6 cm. in size were known. In the U.S.A., in Colorado, they discovered crystal anatase up to 3 cm. in size at the Old Lot deposit, and Vulcan; as well as at deposits of North Carolina, Massachusetts and other states. In Brazil, anatase is extracted at placers of Minas Gerais together with diamond.

Synonyms. Dauphinite, after the discovery location in the Dauphine Prov., France | Oisanite, after the discovery location in Bourg d’Oisans, France | Oktaëdrit, after the shape of its crystal, discr. by IMA | Pyramidal titanic ore | Blue schorl | Wiserine, after the Germ. geologist D. Wiser | Xanthotitan.

Cut Gems. Gem-quality crystals are used for faceting. Usually they are not more than 1-2 ct., the biggest faceted anatase was 6 ct.

Brookite (Brookit—Brookite—Ѕрукит) (Soret, 1822), after Henry James Brooke (1771-1857), an Engl. mineralogist. Oxide – TiO2, orthorhombic system. Hardness 5.5-6.5. Density 3.9-4.1. Diamond luster to metallic one. Comparatively rare mineral, which is usually represented with lamellar crystals of yellow-brown, and reddish-brown color. Inclusions of small lamellar crystals of brookite in hypersthene produce asterism in it. Columnar or bipyramidal variety of brookite – arkansite of completely black hue. Lamellar brookite, as well as anatase, is found mainly in alpine veins.

In Russia, the biggest plate crystals of brookite, up to 4x3x0.3 cm, were found in the Subpolar Urals Mts., at the deposits Omega-Shor and Central Patok, in the upper reaches of the Great Patok River (the basin of the Pechora River). In the South Urals, hyacinth-red crystals of brookite, 8x9x3.5 mm. were extracted at the Atlyanskii placer, near of Miass, and at the Kochkar’ placers, near of Plast. In Yakutia, in metasomatics of the Murun alkali massif, they found crystals of arkansite up to 2 cm. available for faceting. Similar crystals are known in alpine veins of the Bourg d’Oisans deposit, France; and in Switzerland at the Piz Ault deposit, Graubünden canton, and near Maderanertal, where their size was up to 4 cm. In the U.S.A., crystals of brookite up to 4 cm. at the Magnet Cove deposit, Hot Springs Co., Arkansas, were found.

Synonyms. Arkansite, after the discovery location in the Arkansas state, the U.S.A. | Eumanite | Jurinite, after the Swedish researcher of the nature L. Jurene.

Cut Gems. The flattened shape of crystals of brookite gives a possibility to use them mainly as flat insets, beautiful in gleam, because of sector dispersion of color.

 

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