Inosilicates contain two important rock-forming mineral groups ; single-chain silicates are most commonly pyroxenes, while double-chain silicates are often amphiboles.

Peridotites have two primary modes of origin, as mantle rocks formed during the accretion and differentiation of the Earth, or as cumulate rocks formed by precipitation of olivine ± pyroxenes from basaltic or ultramafic magmas ; these magmas are ultimately derived from the upper mantle by partial melting of mantle peridotites.

Despite its chemical similarity to the compositional spectrum of the pyroxene group of minerals — where magnesium and iron substitution for calcium ends with diopside and hedenbergite respectively — it is structurally very different, with a third SiO < sub > 4 </ sub > tetrahedron in the linked chain ( as opposed to two in the pyroxenes ).

Most apparent, in hand specimens, is that amphiboles form oblique cleavage planes ( at around 120 degrees ), whereas pyroxenes have cleavage angles of approximately 90 degrees.

Many, if not most, surface outcrops have been at least partly altered to serpentinite, a process in which the pyroxenes and olivines are converted to green serpentine.

Al-depleted komatiites have been modeled by melting experiments as being produced by high degrees of partial melting of hydrous mantle at low pressure where Al-bearing pyroxenes in the source are not melted, whereas Al-undepleted komatiites are produced by high degree partial melts at greater depth, allowing melting of Al-rich pyroxene.

The principal difference between norite and gabbro, however, is the type of pyroxene of which it is composed ; norite is predominately composed of orthopyroxenes, largely high magnesian enstatites, whereas the principal pyroxenes in gabbro are clinopyroxenes, generally medially iron-rich augites.

It also occurs in igneous and metamorphic rocks chiefly in the silicate minerals: plagioclases, amphiboles, pyroxenes and garnets.

Two-directional cleavage is described as prismatic, and occurs in minerals such as the amphiboles and pyroxenes.

For example, as the amphiboles are double-chain silicates and the pyroxenes are single-chain silicates, the angle between their cleavage planes is different.

Some important rock-forming silicates include the feldspars, quartz, olivines, pyroxenes, amphiboles, garnets, and micas.

Magnesium carbonate and iron oxides with silica crystallize as olivine or enstatite, or with alumina and lime form the complex ferro-magnesian silicates of which the pyroxenes, amphiboles, and biotites are the chief.

With high alkalis, soda-bearing pyroxenes and amphiboles may be present.

Other minerals, such as olivines, pyroxenes, amphiboles, micas, feldspars, and quartz, may be found in metamorphic rocks, but are not necessarily the result of the process of metamorphism.

The chief differences from pyroxenes are that ( i ) amphiboles contain essential hydroxyl ( OH ) or halogen ( F, Cl ) and ( ii ) the basic structure is a double chain of tetrahedra ( as opposed to the single chain structure of pyroxene ).

Although aluminium substitutes extensively for silicon in silicates such as feldspars and amphiboles, the substitution occurs only to a limited extent in most pyroxenes.

The sodium-bearing amphiboles and pyroxenes so characteristic of the phonolites may also be found in some trachytes ; thus aegirine or aegirine augite forms outgrowths on diopside crystals, and riebeckite may be present in spongy growths among the feldspars of the groundmass ( as in the trachyte of Berkum on the Rhine ).

Biotite, sodium rich amphiboles and pyroxenes along with iron rich olivine are common minor minerals.

Some important rock-forming silicates include the feldspars, quartz, olivines, pyroxenes, amphiboles, garnets and micas.

Characteristic primary phases in the groundmass include: zoned pyroxenes ( cores of diopside rimmed by Ti-aegirine ); spinel-group minerals ( magnesian chromite to titaniferous magnetite ); Sr-and REE-rich perovskite ; Sr-rich apatite ; REE-rich phosphates ( monazite, daqingshanite ); potassian barian hollandite group minerals ; Nb-bearing rutile and Mn-bearing ilmenite.

The chain silicate structure of the pyroxenes offers much flexibility in the incorporation of various cations and the names of the pyroxene minerals are primarily defined by their chemical composition.

While still dominated by silicates, more primitive volcanic rocks have mineral assemblages with less silica, such as olivine and the pyroxenes.

Enstatite and the other orthorhombic pyroxenes are distinguished from those of the monoclinic series by their optical characteristics, such as straight extinction, much weaker double refraction and stronger pleochroism.

Type IIE restriction endonucleases ( e. g. NaeI ) cleave DNA following interaction with two copies of their recognition sequence.

Similar to type IIE enzymes, type IIF restriction endonucleases ( e. g. NgoMIV ) interact with two copies of their recognition sequence but cleave both sequences at the same time.

" The tale is told of Joseph Asscher, the greatest cleaver of the day ," wrote Matthew Hart in his book Diamond: A Journey to the Heart of an Obsession, " that when he prepared to cleave the largest diamond ever known, the Cullinan, he had a doctor and nurse standing by and when he finally struck the diamond and it broke perfectly in two, he fainted dead away.

Second, there is a lot of amplification in two stages of classic phototransduction: one pigment will activate many molecules of transducin, and one PDE will cleave many cGMPs.

Another way to view the surface energy is to relate it to the work required to cleave a bulk sample, creating two surfaces.

These two energy quantities refer to the energy that is needed to cleave one species into two pieces while it is contained in a medium of the other species.

Restriction endonucleases or restriction enzymes typically cleave in two ways: blunt-ended or sticky-ended patterns.

The large island is almost divided in two parts by the Gullesfjorden and Kanstadfjorden, and the old name is probably derived from an old verb with the meaning " cleave ", " split ", or " cut ".

The blades are incredibly strong and sharp, and have been shown to be able to cleave rock in two.

There are two major classes of Neuraminidase that cleave exo or endo poly-sialic acids:

The enzyme encoded by this gene contains two C-terminal TS motifs and functions as aggrecanase to cleave aggrecan, a major proteoglycan of cartilage.

Large molecules cleave at their weakest points and produce smaller, more volatile fragments.

Two inlets, Elphinstone ( Khawr ash Shamm ) and Malcom ( Ghubbat al Ghazirah ), cleave the coastline about one third of the distance from the Strait of Hormuz and at one point are separated by only a few hundred meters of land.

* Type I enzymes () cleave at sites remote from recognition site ; require both ATP and S-adenosyl-L-methionine to function ; multifunctional protein with both restriction and methylase () activities.

* Type II enzymes () cleave within or at short specific distances from recognition site ; most require magnesium ; single function ( restriction ) enzymes independent of methylase.

* Type III enzymes () cleave at sites a short distance from recognition site ; require ATP ( but do not hydrolyse it ); S-adenosyl-L-methionine stimulates reaction but is not required ; exist as part of a complex with a modification methylase ().

They recognize and cleave DNA at the same site, and they do not use ATP or AdoMet for their activity — they usually require only Mg < sup > 2 +</ sup > as a cofactor.

Type IIS restriction endonucleases ( e. g. FokI ) cleave DNA at a defined distance from their non-palindromic asymmetric recognition sites.

* Homing endonuclease genes cleave DNA at its own site on the homologous chromosome, triggering the DNA double-stranded break repair system, which " repairs " the break by copying the HEG onto the homologous chromosome.

Many ribozymes have either a hairpin – or hammerhead – shaped active center and a unique secondary structure that allows them to cleave other RNA molecules at specific sequences.

Bacteria have restriction enzymes, also called restriction endonucleases, which cleave double stranded DNA at specific points into fragments, which are then degraded further by other endonucleases.

Some DNases cleave only residues at the ends of DNA molecules ( exodeoxyribonucleases, a type of exonuclease ).

Serine proteases ( or serine endopeptidases ) are enzymes that cleave peptide bonds in proteins, in which serine serves as the nucleophilic amino acid at the ( enzyme's ) active site.

Bromelain prefers to cleave at Lys -, Ala -, Tyr -, Gly -.

Moreover, HindII will only cleave a DNA molecule at this particular site.

Endonucleases are enzymes that cleave the phosphodiester bond within a polynucleotide chain, in contrast to exonucleases, which cleave phosphodiester bonds at the end of a polynucleotide chain.

J Milles, who recorded that " we had not been there above half an hour before we saw it cleave from ye foundations and it fell with such a noise yet was heard at three or four miles ( 5 or 6 km ) distant.

Papain prefers to cleave at: ( hydrophobic )-( Arg or Lys )- cleaves here -( not Val ).

These enzymes are called restriction endonucleases or restriction enzymes, and they are able to cleave DNA molecules at the positions at which particular short sequences of bases are present

A exoglycosidase would remove each carbohydrate monomer ( x ) one by one from the end, starting at xn, whereas and endogylcosidase can cut at any glycosidic bond (-) and may cleave after a signature ' link oligosaccharide ' that links certain carbohydrates to certain proteins.