Ijolite is an

igneous rock Igneous rock ( ), 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 ...

consisting essentially of

nepheline Nepheline, also called nephelite (), is a rock-forming mineral in the feldspathoid groupa silica-undersaturated aluminosilicate, Na3 K Al4 Si4 O16, that occurs in intrusive and volcanic rocks with low silica, and in their associated pegmatit ...

and

augite Augite, also known as Augurite, is a common rock-forming pyroxene mineral with formula . The crystals are monoclinic and prismatic. Augite has two prominent cleavages, meeting at angles near 90 degrees. Characteristics Augite is a solid soluti ...

. Ijolite is a rare rock type of considerable importance from a

mineralogical Mineralogy is a subject of geology specializing in the scientific study of the chemistry, crystal structure, and physical (including optical) properties of minerals and mineralized artifacts. Specific studies within mineralogy include the proces ...

and

petrological Petrology () is the branch of geology that studies rocks, their mineralogy, composition, texture, structure and the conditions under which they form. Petrology has three subdivisions: igneous, metamorphic, and sedimentary petrology. Igneous an ...

standpoint. The word is derived from the first syllable of the Finnish words such as ''Iivaara'', ''

Iijoki Iijoki () is a river of Finland in the region of North Ostrobothnia. The river has many tributaries. Facta (encyclopedia) part 6, page 390, ''finnish'' It flows for into the Gulf of Bothnia. Some of its main tributaries are Siuruanjoki and Livoj ...

'' and '' Ii'', all geographical names in

Finland Finland, officially the Republic of Finland, is a Nordic country in Northern Europe. It borders Sweden to the northwest, Norway to the north, and Russia to the east, with the Gulf of Bothnia to the west and the Gulf of Finland to the south, ...

, and the

Ancient Greek Ancient Greek (, ; ) includes the forms of the Greek language used in ancient Greece and the classical antiquity, ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Greek ...

''Xiflos'', a stone. Ijolite occurs in various parts of the

Kainuu Kainuu (), also historically known as Cajania (), is one of the 19 regions of Finland (''maakunta'' / ''landskap''). Kainuu borders the regions of North Ostrobothnia, North Savo and North Karelia. In the east, it also borders Russia (Republic o ...

region of eastern

and in the

Kola Peninsula The Kola Peninsula (; ) is a peninsula in the extreme northwest of Russia, and one of the largest peninsulas of Europe. Constituting the bulk of the territory of Murmansk Oblast, it lies almost completely inside the Arctic Circle and is border ...

of northwest

Russia Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by area, largest country in the world, and extends across Time in Russia, eleven time zones, sharing Borders ...

on the shores of the

White Sea The White Sea (; Karelian language, Karelian and ; ) is a southern inlet of the Barents Sea located on the northwest coast of Russia. It is surrounded by Karelia to the west, the Kola Peninsula to the north, and the Kanin Peninsula to the nort ...

. Ijolite was first defined and named by Finnish geologist

Wilhelm Ramsay Wilhelm Ramsay (20 January 1865 – 6 January 1928) was a Finnish geologist. He became a member of the Royal Swedish Academy of Sciences in 1914 and in 1915 was accepted into the Royal Physiographic Society in Lund. He coined the terms Fennoscan ...

. The

pyroxene The pyroxenes (commonly abbreviated Px) are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula , where X represents ions of calcium (Ca), sodium (Na), iron ( ...

is , yellow or green, and is surrounded by formless areas of nepheline. The accessory minerals are

apatite Apatite is a group of phosphate minerals, usually hydroxyapatite, fluorapatite and chlorapatite, with high concentrations of Hydroxide, OH−, Fluoride, F− and Chloride, Cl− ion, respectively, in the crystal. The formula of the admixture of ...

cancrinite Cancrinite is a complex carbonate and silicate of sodium, calcium and aluminium with the formula Na6Ca2 water">H2O. It is classed as a member of the feldspathoid group of minerals; the alkali feldspars that are poor in silica. Yellow, orange, pin ...

calcite Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on ...

titanite Titanite, or sphene (), is a calcium titanium nesosilicate mineral, Ca Ti Si O5. Trace impurities of iron and aluminium are typically present. Also commonly present are rare earth metals including cerium and yttrium; calcium may be partly rep ...

and schorlomite, a dark-brown titaniferous variety of melanite-

garnet Garnets () are a group of silicate minerals that have been used since the Bronze Age as gemstones and abrasives. Garnet minerals, while sharing similar physical and crystallographic properties, exhibit a wide range of chemical compositions, de ...

. This rock is the

plutonic Intrusive rock is formed when magma penetrates existing rock, crystallizes, and solidifies underground to form ''intrusions'', such as batholiths, dikes, sills, laccoliths, and volcanic necks.Intrusive RocksIntrusive rocks accessdate: Marc ...

and holo-crystalline analogue of the

nephelinite Nephelinite is a fine-grained or aphanitic igneous rock made up almost entirely of nepheline and clinopyroxene (variety augite). If olivine is present, the rock may be classified as an olivine nephelinite. Nephelinite is dark in color and may rese ...

s -volcanic equivalent and nepheline-dolerites; it bears the same relation to them as the

nepheline syenite Nepheline syenite is a holocrystalline Intrusion, plutonic rock that consists largely of nepheline and alkali feldspar. The rocks are mostly pale colored, grey or pink, and in general appearance they are not unlike granites, but dark green varie ...

s have to the

phonolite Phonolite is an uncommon shallow intrusive or extrusive rock, of intermediate chemical composition between felsic and mafic, with texture ranging from aphanitic (fine-grained) to porphyritic (mixed fine- and coarse-grained). Phonolite is a var ...

s. A

leucite Leucite (from the Greek word ''leukos'' meaning white) is a rock-forming mineral of the feldspathoid group, silica-undersaturated and composed of potassium and aluminium tectosilicate KAlSi2O6. Crystals have the form of cubic icositetrahedra b ...

-augite rock, resembling ijolite except in containing leucite in place of nepheline, is known to occur at Shonkin Creek, near

Fort Benton, Montana Fort Benton is a city in and the county seat of Chouteau County, Montana, United States. Established in 1846, Fort Benton is the oldest continuously occupied settlement in Montana. Fort Benton was the most upstream navigable port on the Miss ...

, and was earlier called missourite, but is now regarded as a variety of

leucitite Leucitite or leucite rock is an igneous rock containing leucite. It is scarce, many countries such as England being entirely without them. However, they are of wide distribution, occurring in every quarter of the globe. Taken collectively, they exhi ...

References

* {{Rock type Plutonic rocks