Tourmalines

Tourmaline is a complicated natrual mineral of the comprehensive chemical formula (Na,Ca)(Mg,Fe)3B3Al6Si6(0,0H,F)si. There are several modifications different in stracture and in doping substances, which cause also different color of this mineral. 

Other tourmaline ciystals contain Cr and Li atoms what make their characteristic color. Tourmaline ciystals doped by Fe are black. 

Tommaline crystals cannot build bicrystals what is especially important in piezoelectric sensors. This property allows for the application of tourmaline sensors in 

Z-cut is the most important in possible applications. Elastic modulus C33 (in the direction of z-cut thickness) is 1.85 times bigger than cn in quartz. Another 

6 Lithium niobate (LiNbOa) and Lithium tautalate (LiTaOa) 

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Dispersion staining is useful for rapid deterrnination of refractive index and dispersion. It is appHed most often, however, for needle-in-a-haystack detection of any particular substance in a mixture such as chrysotile in insulation, cocaine in dust samples, quartz in mine samples, or any particular mineral, eg, tourmaline, in a forensic soil sample. 

Idiochromatic examples of this are black magnetite [1309-38-2] Fe O otherwise written as Fe(II)0 Fe2(111)02 and the analogous red Mn O and the pigments Pmssian blue [14038-43-8] and Turnbull s blue [25869-98-17, both Fe4(III)[Fe(II)(CN)2]2. Allochromatic examples are widespread in the mineral field, with Fe + + Fe + being involved in blue and green tourmaline [1317-93-7] blue iolite (cordierite) [12182-53-5] etc. 

Graupen-erz, n. granular ore. -kobalt, m. smaltite. -schleim, m. barley water, -schorl, m. aphrizite (a black tourmaline). 

Tndig-rot. n. — Indigorot. -stein, m. indicolite (blue tourmaline), -weiss, n. indigo white. 

Strahl-keil, m. belemnite. -kies, m. marcasite. -kondensator, m. jet condenser, -korper, m. radiating body, radiator, -ptimpe, /. jet pump, injector, -punkt, m. radiating point, radiant point, -quarz, m. fibrous quartz, -schdrl, m. radiated tourmaline, -stein, m. actinolite amianthus. 

Since ferrous iron usually colors minerals green, and ferric iron yellow or brown, it may seem rather remarkable that the presence of both together should give rise to a blue color, as in the case of vivianite. It may be pointed out, however, that this is by no means a unique instance of such an effect. Even apart from the artificial substances, Prussian and Turnbull s blues, which are complex cyanides containing both ferric and ferrous iron, there are several blue minerals in which the color seems explainable only on this basis. The most noteworthy of these are crocidolite and related amphiboles iolite and the blue tourmaline or indicolite. Other instances may perhaps be discovered, should this subject ever be investigated as it deserves to be . 

A variety of minerals are prized for their exquisite beauty, rarity, and exceptional durability. These extraordinary materials are classified as gemstones. One such mineral, silica, with a chemical composition of SK>2 (silicon dioxide), exhibits several crystal structures. Several gemstones are crystalline forms of silica, including amethyst, aquamarine, emerald, garnet, peridot, topaz, tourmaline, and zircon J l... 

Treasure Lake Group, overlain by felsic ignimbrite sheets of the Faber Group (Goad et al. 2000). Ore minerals mainly consists of Fe-, As-, Co- and Cu-sulphides, native Au and Bi. Intense, pervasive, polyphase iron-oxide (magnetite-dominant)-hornblende-biotite-tourmaline-K-feldspar-carbonate replacive alteration occurs in the upper metasedimentary sequence below the volcanic-sedimentary unconformity... 

Tourmaline occurs in three bedrock samples in considerable amounts (up to 650 grains/sample) but in two of these samples, both from barren brecciated porphyry, tourmaline occurs as very small grains (<0.05 mm) intercalated with quartz so that few grains are heavier than 3.2 g/cm3 in the 0.25-0.5 mm fraction. The fragmental nature of the tourmaline grains in crackle breccias hampers the use of tourmaline as an indicator mineral for the NICO deposit. 

Placer deposits, in general conglomerates, which contain quartz, sericite, chlorite, tourmaline and sometimes rutile and graphite. Gold can be coarse. Some deposits contain up to 3% pyrite. Size ofthe gold contained in pyrite ranges from O.Olto 0.07 pm... 

Disseminated deposits. In these deposits, the cassiterite grains range from 0.2 to 0.001mm. Cassiterite is mostly dispersed in gangue matrix of alumosilicates, tourmaline and quartz. Recovery of cassiterite from these deposits is quite difficult. 

Depending on the composition of disseminated and medium-coarse-grained ore, they can be divided into two basic groups sulphides and chloritic tourmaline ores. In the sulphide ore, the minerals are represented by pyrite, pyrrhotite, arsenopyrite, chalcopyrite, galena and stannin. Less common are sphalerite and bismuth. 

The chloritic tourmaline ore type contains significant quantities of ferrosilicates, tourmaline and chlorites. 

Some gangue minerals such as tourmaline and topaz often occur associated with cassiterite ore. The separation of topaz and tourmaline is particularly troublesome since... 

Quartz Mica Feldspar Tourmaline Topaz Fe203 Garnet Tautalite... 

Studies carried out on ore that contains topaz and tourmaline [15] indicate that tourmaline and topaz can be floated ahead of cassiterite using dodecil amine hydrochloride as collector. The citric acid can be used to activate both topaz and tourmaline in a pH range from 2.9 to 5.8. Topaz may be selectively activated by fluoride and phosphate ions. 

Moderately difficult floating ores - cassiterite sulphide deposits with small quantities of chloritic tourmaline and Fe-oxides are considered to be moderately difficult. 

Difficult-to-float (or sometimes virtually unfloatable) ore - these ores contain large quantities of chlorite, tourmaline, topaz, fluorite and limonite. 

The flotation feed at the Valkoomesky plant contains tourmaline (18%), biotite (13%), muscovite (17%), limonite (2%) and sulphides (5%). Tin assays in the flotation feed averaged about 0.5% Sn, of which the bulk was contained in the -48 to +12 pm fractions. Flotation of tin was carried out with sea water using oxidized petroleum solution in kerosene (1 2 ratio). 

The above collectors showed good selectivity towards tourmaline and muscovite. 

The San Rafael tin mine is one of the richest ore mine in the world, with a head grade of about 5% Sn. The mine actually started in the 1960s as a copper operation, and later tin was discovered and the operation started as a tin operation. The ore is coarse grained, and a portion of the tin was recovered at a relatively coarse-grind size (i.e. 8 mm size). The main gangue minerals found in this ore were silicates, pyrite, pyrrhotite, tourmaline and minor amounts of copper and silver. 

Andrews, P.R.A., Flotation Characteristics of Cassiterite, Tourmaline and Topaz, MSC Thesis, University of Melbourne, Australia, 1971. 

Sodium alkyl sulphonate is also a collector for tantalite and columbite at a pH below 3.0 (Figure 23.2). At a pH above 3.0, flotation recovery of tantalite and columbite decreased rapidly. This collector was not selective towards gangue minerals, such as tourmaline and garnet. 

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