A phenocryst is an early forming, relatively large and usually conspicuous crystal distinctly larger than the grains of the rock groundmass of an igneous...

layers of materials. Porphyritic texture is one in which larger pieces (phenocrysts) are embedded in a background mass made of much finer grains. Fragmental...

partially resorbed phenocrysts or an accessory phase in basalts generated at depth. Phlogopite mica is a commonly known phenocryst and groundmass phase...

crystals (phenocrysts) formed prior to the extrusion that brought the magma to the surface, embedded in a finer-grained matrix. These phenocrysts usually...

crystals (phenocrysts) of plagioclase formed prior to the extrusion that brought the magma to the surface, embedded in a finer-grained matrix. Phenocrysts of...

common in American usage, while amygdale is more common in British usage. Phenocryst – Crystal larger than the rock grains that surround it in an igneous rock...

glass in texture. They often contain clasts of other rocks and phenocrysts. Phenocrysts are crystals that are larger than the matrix and are identifiable...

during eruption. Any larger crystals visible to the human eye, called phenocrysts, form earlier while slowly cooling in the magma reservoir. When igneous...

found in spinel dunite xenoliths from La Palma, Canary Islands. Ecuador: Phenocrysts found in alkaline extrusive rocks (tephrite), product of effusive volcanism...

rocks – An ultramafic, ultrapotassic intrusive rock dominated by mafic phenocrysts in a feldspar groundmass Latite – Type of volcanic rock – A silica-undersaturated...

difference in size between the tiny matrix crystals and the much larger phenocrysts. Porphyries may be aphanites or phanerites, that is, the groundmass may...

peppering the lighter color minerals. Occasionally some individual crystals (phenocrysts) are larger than the groundmass, in which case the texture is known as...

(SiO2=bulk 67.5–68.5% (dacite), matrix 75–76% (rhyolite) and consistent phenocryst content (35–50%) and mineralogical composition (plagioclase, sanidine...

tendency to form phenocrysts. Higher iron and magnesium tends to manifest as a darker groundmass, including amphibole or pyroxene phenocrysts. Mafic or basaltic...

may contain phenocrysts of mafic minerals, usually hornblende, pyroxene or a feldspar mineral, and may need to be named after their phenocryst mineral, such...

Rhomb porphyry is an example with usually large porphyritic rhomb shaped phenocrysts embedded in a very fine-grained matrix. Some of the best known trachytes...

porphyry. Porphyritic texture develops when the larger crystals, called phenocrysts, grow to considerable size before the main mass of the magma crystallizes...

belonging to the "lamprophyre facies" are characterized by the presence of phenocrysts of mica and/or amphibole together with lesser clinopyroxene and/or melilite...

ago. Tephriphonolite to phonolite lavas "characterized by rhomb mega-phenocrysts of sodic feldspars" of the Rhomb Porphyry group, dated to 460,000–360...

biotite found in its volcanic equivalent, rhyolite. Biotite is an essential phenocryst in some varieties of lamprophyre. Biotite is occasionally found in large...

difference in the size of mineral crystals, with the larger crystals known as phenocrysts. Both extrusive and intrusive rocks can be porphyritic, meaning all types...

from volcanic flows containing significant accumulations of magnetite phenocrysts. Chilean magnetite iron ore deposits within the Atacama Desert have also...

finer-grained, often microscopic, crystals in which larger crystals, called phenocrysts, are embedded. This porphyritic texture is indicative of multi-stage...

very rich in the mineral olivine. It is dark with yellow-green olivine phenocrysts (20-50%) and black to dark brown pyroxene, mostly augite. The olivine-rich...

appear to have a common origin and define an alkaline–peralkaline suite. Phenocrysts include mainly plagioclase, with less common olivine and titanomagnetite;...

fragments are commonly blown apart by the explosive eruption. Most are phenocrysts that grew in the magma, but some may be exotic crystals such as xenocrysts...

The lithology of this porphyritic basalt is characterized by olivine and augite phenocrysts....

separate calc-alkaline rocks with oligoclase phenocrysts (dacites) from rocks with orthoclase phenocrysts (rhyolites). Dacite consists mostly of plagioclase...

in the fine groundmass, or matrix. The larger inclusions are called phenocrysts. They consist essentially of very small crystals of minerals such as...

texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained groundmass. The mineral assemblage is predominantly...