RhyoliteRhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained groundmass. The mineral assemblage is predominantly quartz, sanidine, and plagioclase. It is the extrusive equivalent of granite. Its high silica content makes rhyolitic magma extremely viscous.
Igneous rockIgneous rock ( from Latin'fiery'), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rocks are formed through the cooling and solidification of magma or lava. The magma can be derived from partial melts of existing rocks in a terrestrial planet's mantle or crust. Typically, the melting is caused by one or more of three processes: an increase in temperature, a decrease in pressure, or a change in composition.
FeldsparFeldspar ( ; sometimes spelled felspar) is a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the plagioclase (sodium-calcium) feldspars and the alkali (potassium-sodium) feldspars. Feldspars make up about 60% of the Earth's crust and 41% of the Earth's continental crust by weight.
PyroxeneThe pyroxenes (commonly abbreviated Px) are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks.
PantelleritePantellerite is a type of volcanic rock, specifically a peralkaline rhyolite. It has a higher iron and lower aluminium composition than comendite. It is named after Pantelleria, a volcanic island in the Strait of Sicily and the type location for this rock. On Pantelleria the rock is usually found as a vitrophyre containing phenocrysts of anorthoclase or sanidine. Quartz is found only in the most strongly peralkaline rocks.
AmphiboleAmphibole ( ) is a group of inosilicateminerals, forming prism or needlelike crystals, composed of double chain SiO4tetrahedra, linked at the vertices and generally containing ions of iron and/or magnesium in their structures. Its IMAsymbol is Amp. Amphiboles can be green, black, colorless, white, yellow, blue, or brown. The International Mineralogical Association currently classifies amphiboles as a mineral supergroup, within which are two groups and several subgroups.
ComenditeComendite is a hard, peralkalineigneous rock, a type of light blue grey rhyolite. Phenocrysts are sodic sanidine with minor albite and bipyramidal quartz. The blue colour is caused by very small crystals of riebeckite or arfvedsonite. The 1903 eruption of Changbaishan volcano in northeast China erupted comendite pumice. Comendite derives its name from the area of Le Commende on San Pietro Island in Italy, where the rock type is found.
SodiumChemical element with atomic number 11 (Na)Li↑Na↓Kneon ← sodium → magnesium
RiebeckiteRiebeckite is a sodium-rich member of the amphibole group of silicate minerals. It has chemical formula Na2(Fe3Fe2)Si8O22(OH)2. It forms a solid solution series with magnesioriebeckite, where Mg substitutes for Fe. It crystallizes in the monoclinic system, usually as long prismaticcrystals showing a diamond-shaped cross section, but also in fibrous, bladed, acicular, columnar, and radiating forms. Its Mohs hardness is 5.0–6.0, and its specific gravity is 3.0–3.4.
AluminiumB↑Al↓Gamagnesium ← aluminium → silicon
PotassiumNa↑K↓Rbargon ← potassium → calcium
AegirineAegirine is a mineral. It is a member of the clinopyroxene group of inosilicate minerals. Acmite is a fibrous green-colored variety of aegirine, with the name also used as a synonym. It was first described in 1821, in Kongsberg, Norway. EtymologyThe name aegirine is derived from Ægir , a Norse mythological figure (god of the sea), as the mineral was first described from Norway.*As an Amazon Associate I earn from qualifying purchases.