Search results
Results From The WOW.Com Content Network
Hornblende is a complex inosilicate series of minerals. [6] It 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. Hornblende minerals are common in igneous and metamorphic rocks. The general formula is (Ca,Na) 2−3 (Mg,Fe,Al) 5 (Al,Si) 8 O 22 (OH,F) 2.
Although tremolite is a metamorphic amphibole, it is most commonly derived from highly metamorphosed ultramafic rocks, and thus tremolite-talc schist is not generally considered a variety of amphibolite. A holocrystalline plutonic igneous rock composed primarily of hornblende amphibole is called a hornblendite, which is usually a crystal ...
Amphibole (/ ˈ æ m f ə b oʊ l / AM-fə-bohl) is a group of inosilicate minerals, forming prism or needlelike crystals, [1] composed of double chain SiO 4 tetrahedra , linked at the vertices and generally containing ions of iron and/or magnesium in their structures.
Hornblendite from Poland. Hornblendite is a plutonic rock consisting mainly of the amphibole hornblende. Hornblende-rich ultramafic rocks are rare and when hornblende is the dominant mineral phase they are classified as hornblendites with qualifiers such as garnet hornblendite identifying a second abundant contained mineral.
Pargasite or pargasitic hornblende is a complex inosilicate mineral of the amphibole group with formula NaCa 2 (Mg 4 Al)(Si 6 Al 2)O 22 (OH) 2. It was first described for an occurrence in Pargas, Finland in 1814 and named for the locality. [6] It occurs in high temperature regional metamorphic rocks and in the skarns within contact aureoles ...
The hornblende-hornfels facies is a facies with the same low pressures but slightly higher temperatures as the albite-epidote facies. Though it is named for the mineral hornblende, the appearance of that mineral is not constrained to this facies. The hornblende-hornfels facies has the following mineral assemblages: In metabasites:
The reaction rim constituted by amphibole and/or biotite is commonly observed. The amphibole is of high alkali, such as alkaline hornblende and riebeckite. The alkaline clinopyroxene and amphibole are characteristics of typical alkaline rocks. Biotite is annite, with high Fe/Mg ratio.
The endmember hornblende tschermakite (☐Ca 2 (Mg 3 Al 2)(Si 6 Al 2)O 22 (OH) 2) is a calcium rich monoclinic amphibole mineral. It is frequently synthesized along with its ternary solid solution series members tremolite and cummingtonite so that the thermodynamic properties of its assemblage can be applied to solving other solid solution series from a variety of amphibole minerals.