Volcanic pipes or volcanic conduits are subterranean geological structures formed by the violent, supersonic eruption of deep-origin volcanoes.They are considered to be a type of diatreme.Volcanic pipes are composed of a deep, narrow cone of solidified magma (described as "carrot-shaped"), and are usually largely composed of one of two characteristic rock types — …

Phlogopite is a yellow, greenish, or reddish-brown member of the mica family of phyllosilicates.It is also known as magnesium mica.. Phlogopite is the magnesium endmember of the biotite solid solution series, with the chemical formula KMg 3 AlSi 3 O 10 (F,OH) 2.Iron substitutes for magnesium in variable amounts leading to the more common biotite with higher iron content.

Description. L'andésite, comme la plupart des roches volcaniques, présente une structure microlitique [1].Les andésites sont souvent riches en phénocristaux de feldspaths plagioclase et de minéraux ferromagnésiens (hornblende brune, pyroxènes, amphiboles…), noyés dans une pâte appelée verre [1].. L'andésite est l'équivalent volcanique de la diorite plutonique [2].

Moissanite (/ ˈ m ɔɪ s ə ˌ n aɪ t /) is naturally occurring silicon carbide and its various crystalline polymorphs.It has the chemical formula SiC and is a rare mineral, discovered by the French chemist Henri Moissan in 1893. Silicon carbide is useful for commercial and industrial applications due to its hardness, optical properties and thermal conductivity

Crater of Diamonds State Park is a 911-acre (369 ha) Arkansas state park in Pike County, Arkansas, in the United States.The park features a 37.5-acre (15.2 ha) plowed field, the world's only diamond-bearing site accessible to the public.Diamonds have continuously been discovered in the field since 1906, including the Strawn-Wagner Diamond. The site became a state park in …

Ultramafic rocks (also referred to as ultrabasic rocks, although the terms are not wholly equivalent) are igneous and meta-igneous rocks with a very low silica content (less than 45%), generally >18% MgO, high FeO, low potassium, and are composed of usually greater than 90% mafic minerals (dark colored, high magnesium and iron content). The Earth's mantle is …

The Argyle Diamond Mine was a diamond mine located in the East Kimberley region in the remote north of Western Australia.Argyle was at times the largest diamond producer in the world by volume (14 million carats in 2018), although the proportion of gem-quality diamonds was low.It was the only known significant source of pink and red diamonds (producing over 90% of the …

Le basalte est une roche magmatique volcanique issue d'un magma refroidi rapidement et caractérisée par sa composition minéralogique : plagioclases (50 %), de pyroxènes (25 à 40 %), d'olivine (10 à 25 %), et de 2 à 3 % de magnétite.Sur Terre, il a une origine volcanique et est un des constituants principaux de la croûte océanique.Sur la Lune, il constitue la surface des …

Masa diamantului este exprimată în carate, un carat corespunzând cu 0,200 grame.. Pe lângă cristalele de diamant din sistemul cubic, uneori se pot întâlni diamante cu cristale hexagonale denumite Lonsdaleit, unii consideră, aceste diamante s-au format în medii nefavorabile.Duritatea extremă a diamantului este explicată prin legătura stabilă simetrică dintre atomii de carbon.

Diamond is a solid form of pure carbon with its atoms arranged in a crystal. Solid carbon comes in different forms known as allotropes depending on the type of chemical bond. The two most common allotropes of pure carbon are diamond and graphite.In graphite the bonds are sp 2 orbital hybrids and the atoms form in planes, with each bound to three nearest neighbors 120 …