Bytownite is a

calcium Calcium is a chemical element with the symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar ...

rich member of the

plagioclase Plagioclase is a series of tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continuous solid solution series, more p ...

solid solution series of

feldspar Feldspars are 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) felds ...

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...

s with composition between

anorthite Anorthite is the calcium endmember of the plagioclase feldspar mineral series. The chemical formula of pure anorthite is Ca Al2 Si2O8. Anorthite is found in mafic igneous rocks. Anorthite is rare on the Earth but abundant on the Moon. Minera ...

and labradorite. It is usually defined as having between 70 and 90% An (formula: (Ca_0.7-0.9,Na_0.3-0.1) l(Al,Si)Si₂O₈. Like others of the series, bytownite forms grey to white triclinic crystals commonly exhibiting the typical plagioclase twinning and associated fine striations. The

specific gravity Relative density, or specific gravity, is the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for liquids is nearly always measured with respect to water at its dens ...

of bytownite varies between 2.74 and 2.75. The refractive indices ranges are nα=1.563 – 1.572, nβ=1.568 – 1.578, and nγ=1.573 – 1.583. Precise determination of these two properties with chemical,

X-ray diffraction X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles ...

, or petrographic analysis are required for identification.

Occurrence

Bytownite is a rock forming mineral occurring in

mafic A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks in ...

igneous rock Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma o ...

s such as

gabbro Gabbro () is a phaneritic (coarse-grained), mafic intrusive igneous rock formed from the slow cooling of magnesium-rich and iron-rich magma into a holocrystalline mass deep beneath the Earth's surface. Slow-cooling, coarse-grained gabbro is ...

s and anorthosites. It also occurs as

phenocryst 300px, feldspathic phenocrysts. This granite, from the Switzerland">Swiss side of the Mont Blanc massif, has large white plagioclase phenocrysts, triclinic minerals that give trapezoid shapes when cut through). 1 euro coins, 1 euro coin (diameter ...

s in mafic volcanic rocks. It is rare in

metamorphic rock Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock (protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, caus ...

s. It is typically associated with

pyroxene The pyroxenes (commonly abbreviated to ''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 calcium (Ca), sodium (Na), iron (Fe I ...

s and

olivine The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers qui ...

. The mineral was first described in 1836

Thomas Thomson Thomas Thomson may refer to: * Tom Thomson (1877–1917), Canadian painter * Thomas Thomson (apothecary) (died 1572), Scottish apothecary * Thomas Thomson (advocate) (1768–1852), Scottish lawyer * Thomas Thomson (botanist) (1817–1878), Scottish ...

, ''Outlines of Mineralogy, Geology, and Mineral Analysis'', vol. I, Baldwin & Cradock, Londres, 1836
p. 372
/ref> and named for an occurrence at

Bytown Bytown is the former name of Ottawa, Ontario, Canada. It was founded on September 26, 1826, incorporated as a town on January 1, 1850, and superseded by the incorporation of the City of Ottawa on January 1, 1855. The founding was marked by a s ...

(now

Ottawa Ottawa (, ; Canadian French: ) is the capital city of Canada. It is located at the confluence of the Ottawa River and the Rideau River in the southern portion of the province of Ontario. Ottawa borders Gatineau, Quebec, and forms the c ...

), Canada. Other noted occurrences in Canada include the Shawmere anorthosite in Foleyet Township,

Ontario Ontario ( ; ) is one of the thirteen provinces and territories of Canada.Ontario is located in the geographic eastern half of Canada, but it has historically and politically been considered to be part of Central Canada. Located in Central Ca ...

, and on Yamaska Mountain, near Abbotsford,

Quebec Quebec ( ; )According to the Canadian government, ''Québec'' (with the acute accent) is the official name in Canadian French and ''Quebec'' (without the accent) is the province's official name in Canadian English is one of the thirte ...

. It occurs on

Rùm Rùm (), a Scottish Gaelic name often anglicised to Rum (), is one of the Small Isles of the Inner Hebrides, in the district of Lochaber, Scotland. For much of the 20th century the name became Rhum, a spelling invented by the former owner, Sir ...

island,

Scotland Scotland (, ) is a country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a border with England to the southeast and is otherwise surrounded by the Atlantic Ocean to ...

and Eycott Hill, near Keswick,

Cumberland Cumberland ( ) is a historic counties of England, historic county in the far North West England. It covers part of the Lake District as well as the north Pennines and Solway Firth coast. Cumberland had an administrative function from the 12th c ...

, England. It is reported from Naaraodal,

Norway Norway, officially the Kingdom of Norway, is a Nordic countries, Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of ...

and in the Bushveld complex of

South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring coun ...

. It is also found in Isa Valley,

Western Australia Western Australia (commonly abbreviated as WA) is a state of Australia occupying the western percent of the land area of Australia excluding external territories. It is bounded by the Indian Ocean to the north and west, the Southern Ocean to t ...

. In the US it is found in the Stillwater igneous complex of Montana; from near Lakeview,

Lake County, Oregon Lake County is one of the 36 counties in the U.S. state of Oregon. As of the 2020 census, the population was 8,160. Its county seat is Lakeview. The county is named after the many lakes found within its boundaries, including Lake Abert, Summ ...

. It occurs in the Lucky Cuss mine,

Tombstone, Arizona Tombstone is a historic city in Cochise County, Arizona, United States, founded in 1877 by prospector Ed Schieffelin in what was then Pima County, Arizona Territory. It became one of the last boomtowns in the American frontier. The town gr ...

; and from the Grants district, McKinley County, New Mexico. In the eastern US it occurs at Cornwall, Lebanon County, Pennsylvania and Phoenixville,

Chester County, Pennsylvania Chester County (Pennsylvania Dutch: ''Tscheschter Kaundi''), colloquially known as Chesco, is a county in the Commonwealth of Pennsylvania. It is located in the Delaware Valley region of the state. As of the 2020 census, the population was 53 ...

References

* Hurlbut, Cornelius S.; Klein, Cornelis, 1985, ''Manual of Mineralogy'', 20th ed., Wiley,

External links

{{Cite EB1911, wstitle=Bytownite Tectosilicates Calcium minerals Sodium minerals Feldspar Triclinic minerals Gemstones Minerals in space group 2 fr:Bytownite