hornblende

hornblendic, adj.
/hawrn"blend'/, n.
a dark-green to black mineral of the amphibole group, calcium magnesium iron and hydroxyl aluminosilicate.
[1760-70; < G; see HORN, BLENDE]

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Any of a subgroup of amphibole minerals that are calcium-iron-magnesium-rich and monoclinic in crystal structure.

Hornblende, whose generalized chemical formula is (Ca,Na)2(Mg,Fe,Al)5(Al,Si)8O22(OH)2, occurs widely in metamorphic and igneous rocks. Common hornblende is dark green to black in colour and usually found in middle-grade metamorphic rocks (formed under medium conditions of temperature and pressure). Such metamorphic rocks with abundant hornblende are called amphibolites.

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      calcium-rich amphibole mineral that is monoclinic in crystal structure. Hornblende's generalized chemical formula is (Ca,Na)2(Mg,Fe,Al)5(Al,Si)8O22 (OH)2. The four end-members and the cation content of their respective compositions are as follows: hornblende, Ca2(Mg4Al) (Si7Al); tschermakite, Ca2(Mg3Al2)(Si6Al2); edenite, NaCa2(Mg)5(Si7Al); pargasite, NaCa2 (Mg4Al)(Si6Al2). Extensive solid solution occurs, and each end-member has iron-rich equivalents; minor elements, including manganese, titanium, chromium, potassium, fluorine, and yttrium, are usually present. Hornblendes exhibit typical amphibole structures; these are based on double tetrahedral chains between which four metal sites are located. Tetrahedral substitution of aluminum for silicon is common and provides charge balance for trivalent and univalent substitution in the metal sites. For detailed physical properties of hornblende, see amphibole (table).

      Hornblende occurs widely in metamorphic and igneous rocks. Pargasite occurs in high-grade metamorphic rocks that tend to have more aluminum. Metamorphic rocks with abundant hornblende are called amphibolites (amphibolite).

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Universalium. 2010.

Look at other dictionaries:

  • hornblende — [ ɔrnblɛ̃d ] n. f. • 1775; all. Hornblende, de Horn « corne », parce que ces blendes ont l apparence de la corne, et Blende ♦ Minér. Minéral noir ou vert foncé, silicate de fer, d aluminium et de magnésium, appartenant au groupe des amphiboles.… …   Encyclopédie Universelle

  • Hornblende — Amphibole Hornblende General Category Igneous, metamorphic Chemical formula Ca2 …   Wikipedia

  • Hornblende — Catégorie IX : silicates[1] Hornblende Général …   Wikipédia en Français

  • Hornblende — (Amphibol), Mineral, Silikate von Tonerde, Kalk, Magnesia, Eisenoxydul in wechselnder Mischung, ähnlich wie Augit zusammengesetzt und wie dieser auch kristallisierend. Nur bilden die Flächen des Prisma an der Kante einen Winkel von 124° 30 ,… …   Lexikon der gesamten Technik

  • Hornblende — Horn blende , n. [G., fr. horn horn + blende blende.] (Min.) The common black, or dark green or brown, variety of amphibole. (See {Amphibole}.) It belongs to the aluminous division of the species, and is also characterized by its containing… …   The Collaborative International Dictionary of English

  • Hornblende — (Amphibol), Mineral, krystallisirt in Säulen des monoklinoëdrischen Systems, welche theils eingewachsen, theils aufgewachsen u. zu Drusen vereinigt erscheinen, häufig sind Zwillingskrystalle; meist in derben stänglichen od. fasrigen, auch… …   Pierer's Universal-Lexikon

  • *hornblende — ● hornblende nom féminin (allemand Hornblende, de Horn, corne, et blenden, briller) Silicate naturel d aluminium, de calcium, de fer et de magnésium, appartenant au groupe des amphiboles. (On la trouve dans les roches plutoniques [diorites,… …   Encyclopédie Universelle

  • hornblende — 1796, from Ger. Hornblende, from horn (see HORN (Cf. horn) (n.)) + blende (see BLENDE (Cf. blende)) …   Etymology dictionary

  • Hornblende — (Amphibol), Repräsentant einer Gruppe von Mineralien, Silikaten, die in mancherlei Beziehungen zu den Augitmineralien stehen (vgl. Augit, woselbst auch Näheres über die chemische Zusammensetzung und die Kristallisation der H. mitgeteilt ist). Die …   Meyers Großes Konversations-Lexikon

  • Hornblende — Hornblende, Amphibol, monoklines Mineral [häufigste Kristallform Abb. 827], hauptsächlich aus Kieselsäure, Tonerde, Kalk, Magnesia und Eisenoxydul bestehend, weiß bis hellgrün (Grammatit, Tremolit), lauchgrün (Strahlstein oder Aktinolith),… …   Kleines Konversations-Lexikon

  • Hornblende — (Amphibol), Mineral. Zu den Arten der H. gehören der Tremolith, der Strahlstein, die basaltische und gemeine H. und der Anthophillit. Die H. krystallisirt im zwei und eingliederigen System, besteht aus dreifach kieselsaurem Kalk, verbunden mit… …   Herders Conversations-Lexikon

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