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Related to hornblende: tremolite, augite, biotite


see amphiboleamphibole
, any of a group of widely distributed rock-forming minerals, magnesium-iron silicates, often with traces of calcium, aluminum, sodium, titanium, and other elements.
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(1) The most common rock-forming mineral of the group of monoclinic amphiboles (common hornblende). Its approximate chemical composition is Ca2Na[Mg, Fe]4[Al,-Fe][(Si, Al)4O11]2[OH, F]2, with substantial variations in the ratios of basic components and with various element impurities (Na <- K, Ba, Rb; Ca ← TR, Y, Sr, U, W, Mo; Al ← Ga; Mg ← Li; Fe ← Zn, Sc). Hornblende crystallizes in the monoclinic system. It forms long, prismatic needles, irregular grains, and fibrous aggregates of green, black, or brown color. It has a hardness of 5.5–6 on Mohs’ scale and a density of 3,100–3,300 kg/m3. Hornblende is characterized by two directions of well-developed cleavages intersecting at an angle of 124°.

Common hornblende is characteristic of intrusive rocks (granodiorites, syenites, diorites, hornblende gabbros), effusive rocks (andesites, basalts, porphyrites), and metamorphic (am-phibolites, hornblende gneisses) rocks. Common hornblende is a relatively stable mineral, but when acted upon by hydrothermal solutions it alters to chlorite, epidote, calcite, and quartz. In the process of weathering, it decomposes to form opal, carbonates, and various other minerals.

(2) The subgroup of calcium aluminiferous amphiboles that includes common hornblende, edenite, oligoclase, pargasite, and hastingsite.


Deer, W. A., R. A. Howie, and J. Zussmann. Porodoobrazuiushchie mineraly, vol 2. Moscow, 1965. (Translated from English.)
Lodochnikov, V. N. Glavneishie porodoobrazuiushchie mineraly, 5th ed. Moscow, 1974.



A general name given to the monoclinic calcium amphiboles that form an extensive solid-solution series between the various metals in the generalized formula (Ca,Na)2(Mg,Fe,Al)5(Al,Si)8O22(OH,F)2.


a black or greenish-black mineral of the amphibole group, found in igneous and metamorphic rocks. Composition: calcium magnesium iron sodium aluminium aluminosilicate. General formula: (Ca,Na)2.3(Mg,Fe,Al)5Si6(Si,Al)2O22(OH)2
References in periodicals archive ?
Garnet-bearing amphibole schists exhibit schistose structure defined by the alignment of actinolite, hornblende and chlorite and granonematoblastic and locally porphyroblastic and poiquiloblastic textures.
39]Ar hornblende cooling ages of 555 [+ or -] 5 Ma apparently from the Marble Mountain biotite granodiorite unit (based on approximate location shown by Keppie et al.
The presence of euhedral zircon and hornblende (Plates 2 to 6) indicate that ash falls have contributed to this sandstone.
Ectomycorrhizal weathering of the soil minerals muscovite and hornblende.
M]) of the rocks, and single crystal magnetic properties, we have made the following assumptions: 1) magnetic susceptibility of LF2 metabasite is dominated by a paramagnetic contribution which may be dominated by hornblende AMS ([k.
Gravel did show the lowest phosphorus removal efficiency (21%) followed by ironstone and hornblende both with a 33% efficiency.
An inclusion made of hornblende, a group of silicate minerals, yielded similar results.
Back then, "with no headlands to bump into, the beach sand was free to move, allowing the zircon, pink garnet, green hornblende and other minerals eroding off of southern Oregon's Klamath Mountains to move north and mingle with flecks of dark green augite and brown hornblende sifting down the rivers draining the central Coast Range," she writes.
The K-Ar cooling age for hornblende will normally be older than the cooling age for biotite from the same rock, and from those ages one can calculate the approximate rate of uplift from 16 to 11 kilometers for the rock body in question.