Pyroxene group

The pyroxene group of minerals, where cations substitute one for another at interchain sites, also have a tetrahedral Si site that may contain Al. Some of these substitutions, especially those at M2, can distort the ideal crystal structures, as is depicted in Fig. 2.10. The small distortions are detected as variations in bond lengths between adjacent atoms during crystal structure analyses. These data, combined with accurate composition analyses, could indicate some of the conditions present during growth of the crystal and contribute to our understanding of why some mineral species have formed as fibers. Unfortunately, few detailed crystal structural analyses have been performed on pyroxene minerals with fibrous habits. 

Pallasites - main-group, Eagle Station-group, pyroxene-group... 

For descriptions of members of the pyroxene group, see also Acmite-Aegerine Augile Diallage Diopslde Enslalite Hypersthene Jadeiie and Spodumene. 

Spectra of chain silicates Pyroxene group 5.5.1 Background... 

Inosilicates contain single or double chains of tetrahedra. In a single chain structure, the Si to O ratio is 1 3, and in a double chain, it is 4 11. This structural class contains many common rock-forming minerals, including the amphibole and pyroxene groups. Both jade minerals, jadeite, and nephrite, fall within this group. 

Inosilicate Pyroxene group Diopside Cr-diopside (violan) CaMg(SiOs)2 c,gr,br,y,bk 3.25-3.35 1.66-1.75 5-6 Two directional poor cleavage... 

Some of the most common igneous minerals are quartz, potassium feldspars (orthoclase and microcline), plagioclase feldspars (albite, anorthite), micas (muscovite, biotite), olivine, and members of the amphibole and pyroxene groups. Many other minerals are found in igneous rocks, most of which occur in only very small amounts. These are called accessory minerals, the most common of these are corundum, pyrite, magnetite, zircon, rutile, apatite, and members of the garnet group. 

The pyroxene group and the amphibole group, respectively, are representatives of silicate minerals having single-chain and double-chain tetrahedral networks. Pyroxenes are believed to be significant components of Earth s mantle, whereas amphiboles are dark-colored minerals commonly found in continental rocks. 

Enstatite The Mg-rich pyroxene group endmember mineral with the formula MgSiOs. 

The ionsilicates (chain silicates) are comprised of either single or double chains of linked silica tetrahedrons. The single chains (pyroxene group) have the formula and consist of a chain of tetrahedrons that are linked together by two of their corner oxygens. The double chains (amphibole group) have the formula... 

These minerals have the general formula ABSi Og, where A = Ca, Na, Mg, Fe, and B = Mg, Fe +, Fe +, Cr, Mn, Al, with silicon sometimes replaced in part by aluminum. Pyroxenes may crystallize in the orthorhombic or monoclinic systems and occur as short, stout prismatic crystals. Specific mineral examples from the pyroxene group are augite (Mg,Fe,Ca)SiOj and hedenbergite CaFe(Si03)2 (Figure M60). 

Subgroups are sometimes necessary, such as clinopyroxene and orthopyroxene in the pyroxene group, or plagioclase which has six different species and belongs to the feldspar group. 

Iron group Silicates group Pyroxene group Augite Green earth Clark et al. (1969) Rutley (1988)... 

Pyroxene group (Chaiti silicates) Aegirine Augite Diopside Enstatite (Wollastonite). 

Crystalline rock with vitreous pulp and with basic pyroxene groups... 

Pyroxene group of important rock-forming silicate minerals found in many igneous and metamorphic rocks presence in volcanic lavas, where they are sometimes seen as crystals embedded in volcanic glass. 

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