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Encyclopedia > Hornblende
Amphibole (Hornblende)
Amphibole (Hornblende)

Hornblende is a complex inosilicate series of minerals. Hornblende is not a recognized mineral, in its own right but the name is used as a general or field term, to refer to a dark amphibole. It is an isomorphous mixture of three molecules; a calcium-iron-magnesium silicate, an aluminium-iron-magnesium silicate and an iron-magnesium silicate. Manganese, titanium and sodium are sometimes present. Fluorine often substitutes for the hydroxyl in the structure. The general formula can be given as (Ca,Na)2-3(Mg,Fe,Al)5(Al,Si)8O22(OH,F)2. Hornblende has a hardness of 5 - 6, a specific gravity of 2.9 - 3.4 and is typically an opaque green, greenish-brown, brown or black colour. Its cleavage angles are at 56 and 124 degrees. It is most often confused with the minerals augite and biotite mica, both of which are black and can be found in granite and in charnockite. Amphibole (Hornblende) Source: US Government File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Amphibole (Hornblende) Source: US Government File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... For the logical fallacy, see Amphibology. ... The silicate minerals make up the largest and most important class of rock-forming minerals. ... Minerals are natural compounds formed through geological processes. ... For the logical fallacy, see Amphibology. ... In chemistry, a molecule is an aggregate of two or more atoms in a definite arrangement held together by chemical bonds [1] [2] [3] [4] [5]. Chemical substances are not infinitely divisible into smaller fractions of the same substance: a molecule is generally considered the smallest particle of a pure... General Name, Symbol, Number calcium, Ca, 20 Chemical series alkaline earth metals Group, Period, Block 2, 4, s Appearance silvery white Atomic mass 40. ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Atomic mass 55. ... General Name, Symbol, Number magnesium, Mg, 12 Chemical series alkaline earth metals Group, Period, Block 2, 3, s Appearance silvery white Atomic mass 24. ... General Name, Symbol, Number aluminium, Al, 13 Chemical series poor metals Group, Period, Block 13, 3, p Appearance silvery Atomic mass 26. ... General Name, Symbol, Number manganese, Mn, 25 Chemical series transition metals Group, Period, Block 7, 4, d Appearance silvery metallic Atomic mass 54. ... General Name, Symbol, Number titanium, Ti, 22 Chemical series transition metals Group, Period, Block 4, 4, d Appearance silvery metallic Atomic mass 47. ... General Name, Symbol, Number sodium, Na, 11 Chemical series alkali metals Group, Period, Block 1, 3, s Appearance silvery white Atomic mass 22. ... General Name, Symbol, Number fluorine, F, 9 Chemical series halogens Group, Period, Block 17, 2, p Appearance Yellowish brown gas Atomic mass 18. ... // Hydroxyl group The term hydroxyl group is used to describe the functional group -OH when it is a substituent in an organic compound. ... Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. ... Relative density (also known as specific gravity) is a measure of the density of a material. ... Cleavage, in mineralogy, is the tendency of crystalline materials to split along definite planes, creating smooth surfaces, of which there are several named types: Basal cleavage: cleavage parallel to the base of a crystal, or to the plane of the lateral axes. ... Augite is a mineral described chemically as (Ca, Na)(Mg, Fe, Al)(Al, Si)2O6 or calcium sodium magnesium iron aluminium silicate. ... A Biotite slice Biotite is a common phyllosilicate mineral that contains potassium, magnesium, iron and aluminium. ... Quarrying granite for the Mormon Temple, Utah Territory. ... Charnockite is a series of foliated metamorphosed igneous rocks of wide distribution and great importance in India, Ceylon, Madagascar and Africa. ...


Hornblende is a common constituent of many igneous and metamorphic rocks such as granite, syenite, diorite, gabbro basalt, andesite, gneiss and schist. It is the principal mineral of amphibolites. Very dark brown to black hornblendes that contain titanium are ordinarily called basaltic hornblende, from the fact that they are usually a constituent of basalt and related rocks. Hornblende alters easily to chlorite and epidote. A variety of hornblende that contains less than 5% of iron oxides is gray to white in color and named edenite, from its locality in Edenville, New York. Other minerals in the hornblende series include: pargasite, hastingsite and tschermakite. Volcanic rock on North America Plutonic rock on North America Igneous rocks are formed when rock (magma) cools and solidifies, with or without crystallisation, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks. ... Metamorphic rock is the result of the transformation of a pre-existing rock type, the protolith, in a process called metamorphism, which means change in form, derived from the Greek words meta, change, and morphe, form. The protolith is subjected to extreme heat (>150 degrees Celsius) and pressure causing profound... Quarrying granite for the Mormon Temple, Utah Territory. ... Syenite Syenite is a coarse-grained intrusive igneous rock of the same general composition as granite but with the quartz either absent or present in relatively small amounts. ... Categories: Mineral stubs | Igneous rocks ... Gabbro specimen. ... Basalt Columnar basalt at Sheepeater Cliff in Yellowstone Basalt (IPA: ) is a common gray to black volcanic rock. ... A sample of andesite (dark groundmass) with amygdaloidal vesicules filled with zeolite. ... Gneiss Gneiss (IPA: ) is a common and widely distributed type of rock formed by high-grade regional metamorphic processes from preexisting formations that were originally either igneous or sedimentary rocks. ... Schist The schists form a group of medium-grade metamorphic rocks, chiefly notable for the preponderance of lamellar minerals such as micas, chlorite, talc, hornblende, graphite, and others. ... Amphibolite is a gouping of rocks composed mainly of amphibole (as hornblende) and plagioclase feldspars, with little or no quartz. ... Basalt Columnar basalt at Sheepeater Cliff in Yellowstone Basalt (IPA: ) is a common gray to black volcanic rock. ... Chlorite is a group of phyllosilicate minerals often classified as clays. ... Epidote from Slovakia Epidote is a calcium aluminium iron sorosilicate mineral, Ca2(Al, Fe)3(SiO4)3(OH), crystallizing in the monoclinic system. ... Iron oxide pigment There are a number of iron oxides: Iron oxides Iron(II) oxide or ferrous oxide (FeO) The black-coloured powder in particular can cause explosions as it readily ignites. ... NY redirects here. ...


The word hornblende is derived from the German horn and blenden, to 'blind' or 'dazzle'. The term blende is often used to refer to a brilliant non-metallic luster, for example, zincblende and pitchblende, a lustrous form of uraninite. For the file system called Lustre, see Lustre (file system) Lustre (American English: luster) is a description of the way light interacts with the surface of a crystal, rock or mineral. ... General Name, Symbol, Number zinc, Zn, 30 Chemical series transition metals Group, Period, Block 12, 4, d Appearance bluish pale gray Atomic mass 65. ... For the band, see Pitchblende (band). ...


Hornblende is actually the name given to a series of minerals that are rather difficult to distinguish by ordinary means. The iron, magnesium and aluminum ions can freely substitute for each other and form what have been distinguished as seperate minerals. The minerals are given the names Magnesio-hornblende, Ferrohornblende, Alumino-ferro-hornblende and Alumino-magnesio-hornblende. These minerals are obviously named for their chemistries although there is little to distinguish them in the field. The iron rich members of the series are a darker black and less likely to be translucent.


Hornblende is not often a collection mineral because good crystals are somewhat difficult to find even though the mineral is widespread. It is almost always opaque and black and not very attractive. However a few specimens are extraordinary and make for valuable specimens. Some crystals can grow to a fairly large size of several feet long and nearly a foot across. Other specimens of hornblende can be acicular clusters or needle thin crystal aggregates. Many times a specimen of a more valuable mineral will be accented by the opaque black crystals of hornblende.


PHYSICAL CHARACTERISTICS:

 * Color is almost always black to dark green. * Luster is vitreous to dull. * Transparency: Crystals are generally opaque but thin crystals or exceptional specimens can be translucent. * Crystal System is Monoclinic; 2/m * Crystal Habits include short stocky prismatic crystals as well as long thin crystal forms. Crystals can have a hexagonal cross-section although rarely symmetrical. The typical termination, if seen, appears as the two faces of a dome but is actually two of the four faces of a prism. Also found granular, massive and occassionally acicular aggregates. * Cleavage is imperfect in two directions at 56 and 124 degrees. * Fracture is uneven. * Hardness is 5 - 6. * Specific Gravity is approximately 2.9 - 3.4 (somewhat above average for translucent minerals) * Streak is brown to gray. * Other Characteristics: pleochroic in translucent speciments. Large crystals have an almost striated or grainy appearance. * Associated Minerals are quartz, feldspars, augite, magnetite, micas and many medium grade metamorphic minerals. * Notable Occurrences are numerous and include Bancroft, Ontario; Norway; Bohemia; Mt. Vesuvius, Italy and New York, USA. * Best Field Indicators are crystal habit (especially cross-section), color and cleavage. Hornblende is actually the name given to a series of minerals that are rather difficult to distinguish by ordinary means. The iron, magnesium and aluminum ions can freely substitute for each other and form what have been distinguished as seperate minerals. The minerals are given the names Magnesio-hornblende, Ferrohornblende, Alumino-ferro-hornblende and Alumino-magnesio-hornblende. These minerals are obviously named for their chemistries although there is little to distinguish them in the field. The iron rich members of the series are a darker black and less likely to be translucent. 

Hornblende is not often a collection mineral because good crystals are somewhat difficult to find even though the mineral is widespread. It is almost always opaque and black and not very attractive. However a few specimens are extraordinary and make for valuable specimens. Some crystals can grow to a fairly large size of several feet long and nearly a foot across. Other specimens of hornblende can be acicular clusters or needle thin crystal aggregates. Many times a specimen of a more valuable mineral will be accented by the opaque black crystals of hornblende.


PHYSICAL CHARACTERISTICS:

 * Color is almost always black to dark green. * Luster is vitreous to dull. * Transparency: Crystals are generally opaque but thin crystals or exceptional specimens can be translucent. * Crystal System is Monoclinic; 2/m * Crystal Habits include short stocky prismatic crystals as well as long thin crystal forms. Crystals can have a hexagonal cross-section although rarely symmetrical. The typical termination, if seen, appears as the two faces of a dome but is actually two of the four faces of a prism. Also found granular, massive and occassionally acicular aggregates. * Cleavage is imperfect in two directions at 56 and 124 degrees. * Fracture is uneven. * Hardness is 5 - 6. * Specific Gravity is approximately 2.9 - 3.4 (somewhat above average for translucent minerals) * Streak is brown to gray. * Other Characteristics: pleochroic in translucent speciments. Large crystals have an almost striated or grainy appearance. * Associated Minerals are quartz, feldspars, augite, magnetite, micas and many medium grade metamorphic minerals. * Notable Occurrences are numerous and include Bancroft, Ontario; Norway; Bohemia; Mt. Vesuvius, Italy and New York, USA. * Best Field Indicators are crystal habit (especially cross-section), color and cleavage. Hornblende is actually the name given to a series of minerals that are rather difficult to distinguish by ordinary means. The iron, magnesium and aluminum ions can freely substitute for each other and form what have been distinguished as seperate minerals. The minerals are given the names Magnesio-hornblende, Ferrohornblende, Alumino-ferro-hornblende and Alumino-magnesio-hornblende. These minerals are obviously named for their chemistries although there is little to distinguish them in the field. The iron rich members of the series are a darker black and less likely to be translucent. 

Hornblende is not often a collection mineral because good crystals are somewhat difficult to find even though the mineral is widespread. It is almost always opaque and black and not very attractive. However a few specimens are extraordinary and make for valuable specimens. Some crystals can grow to a fairly large size of several feet long and nearly a foot across. Other specimens of hornblende can be acicular clusters or needle thin crystal aggregates. Many times a specimen of a more valuable mineral will be accented by the opaque black crystals of hornblende.


PHYSICAL CHARACTERISTICS:

 * Color is almost always black to dark green. * Luster is vitreous to dull. * Transparency: Crystals are generally opaque but thin crystals or exceptional specimens can be translucent. * Crystal System is Monoclinic; 2/m * Crystal Habits include short stocky prismatic crystals as well as long thin crystal forms. Crystals can have a hexagonal cross-section although rarely symmetrical. The typical termination, if seen, appears as the two faces of a dome but is actually two of the four faces of a prism. Also found granular, massive and occassionally acicular aggregates. * Cleavage is imperfect in two directions at 56 and 124 degrees. * Fracture is uneven. * Hardness is 5 - 6. * Specific Gravity is approximately 2.9 - 3.4 (somewhat above average for translucent minerals) * Streak is brown to gray. * Other Characteristics: pleochroic in translucent speciments. Large crystals have an almost striated or grainy appearance. * Associated Minerals are quartz, feldspars, augite, magnetite, micas and many medium grade metamorphic minerals. * Notable Occurrences are numerous and include Bancroft, Ontario; Norway; Bohemia; Mt. Vesuvius, Italy and New York, USA. * Best Field Indicators are crystal habit (especially cross-section), color and cleavage. 

See also

Gem animals. ...

References


  Results from FactBites:
 
Hornblende (312 words)
Hornblende is not a recognized mineral, but is used as a general or field term to refer to a dark amphibole.
Hornblende is a common constituent of many igneous and metamorphic rocks such as granite, syenite, diorite, gabbro basalt, andesite, gneiss and schist.
Very dark brown to fl hornblendes that contain titanium ordinarily are called basaltic hornblende from the fact that they are usually a constituent of basalt and related rocks.
hornblende.htm (902 words)
The hornblende is associated with plagioclase, biotite and zircon (Wilcox, 1936).
Hornblende is common as small grains in amphibolites and cross-cutting diorite dikes in outcrops along the Chippewa River at Holcombe Dam (SW Sec.
IRON COUNTY: Hornblende is abundant in gneissic and schistose rocks along the west branch of the Montreal River (Van Hise and Irving, 1892).
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