phenocryst

It is an essential phenocryst in some varieties of lamprophyre.

This is why most igneous rocks have only one type of phenocryst mineral.

The usual phenocryst habit is the ones commonly observed.

Classification of andesites may be refined according to the most abundant phenocryst.

Torin manages to serve the guard his "final meal" to get access to the phenocryst's entrance.

A similar type of crystal is a phenocryst, a large crystal in an igneous rock.

Olivine may also be a phenocryst, and when present, may have rims of pigeonite.

So there is an important contrast here between the groundmass of tiny, felted crystals and the much bigger, separate phenocryst minerals.

Porphyritic volcanic rocks are further classified by phenocryst type using mineral name modifiers given in the order of decreasing abundance.

High in fiamme, the third tuff layer differs from the second in that it has even higher phenocryst content, but poor lithics.

A phenocryst is a relatively large and usually conspicuous crystal distinctly larger than the grains of the rock groundmass of a porphyritic igneous rock.

In tholeiitic basalt, pyroxene (augite and orthopyroxene or pigeonite) and calcium-rich plagioclase are common phenocryst minerals.

Phlogopite is encountered as a primary igneous phenocryst within lamproites and lamprophyres, the result of highly fluid-rich melt compositions within the deep mantle.

Chemical classifications are preferred to classify volcanic rocks, with phenocryst species used as a prefix, e.g. "olivine-bearing picrite" or "orthoclase-phyric rhyolite".

Volcanic rocks classified according to the nature and abundance of phenocryst assemblages are often described as aphyric when fewer than 1% phenocrysts are visible with a hand lens.

A quartz latite is a volcanic rock or fine grained intrusive rock equivalent to a latite with a phenocryst modal composition containing 5-20% quartz.

The most abundant phenocryst minerals were hornblende and plagioclase, but an unusual phenocryst mineral was also present-the calcium sulfate, anhydrite.

A typical basalt contains a few per cent of phenocryst minerals, but in an andesite phenocrysts may form as much as 50 per cent volume of the rock.

They briefly had Torin and Leenah held captive but Torin gained their cooperation to access the phenocryst columns to Escarpa and Asthenia.

Phlogopite mica is a commonly known phenocryst and groundmass phase within ultrapotassic igneous rocks such as lamprophyre, kimberlite, lamproite, and other deeply sourced ultramafic or high-magnesian melts.

Also when he helps complete an art installation of Rupert, he receives a royal ball invitation and, lastly, gets a tile piece when Torin discovers a locked gateway to the next phenocryst.

In some cases, felsic volcanic rocks may contain phenocrysts of mafic minerals, usually hornblende, pyroxene or a feldspar mineral, and may need to be named after their phenocryst mineral, such as 'hornblende-bearing felsite'.

Iddingsite forms from the weathering of basalt in the presence of liquid water and can be described as a phenocryst, i.e. it has megascopically visible crystals in a fine-grained groundmass of a porphyritic rock.

The chemistry of the ignimbrites, like all felsic rocks, and the resultant mineralogy of phenocryst populations within them, is related mostly to the varying contents of sodium, potassium, calcium, the lesser amounts of iron and magnesium.

Two things makes this method especially useful; first, clinopyroxene is a common phenocryst in igneous rocks easy to identify, second, the crystallization of the jadeite component of clinopyroxene implies a growth in molar volume being thus a good indicator of pressure.