Sapphirine is a rare

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...

, a

silicate A silicate is any member of a family of polyatomic anions consisting of silicon and oxygen, usually with the general formula , where . The family includes orthosilicate (), metasilicate (), and pyrosilicate (, ). The name is also used ...

magnesium Magnesium is a chemical element; it has Symbol (chemistry), symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 ...

and

aluminium Aluminium (or aluminum in North American English) is a chemical element; it has chemical symbol, symbol Al and atomic number 13. It has a density lower than that of other common metals, about one-third that of steel. Aluminium has ...

, with the

chemical formula A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as pare ...

( (with

iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

as a major impurity). Named for its

sapphire Sapphire is a precious gemstone, a variety of the mineral corundum, consisting of aluminium oxide () with trace amounts of elements such as iron, titanium, cobalt, lead, chromium, vanadium, magnesium, boron, and silicon. The name ''sapphire ...

-like colour, sapphirine is primarily of interest to researchers and collectors: well-formed

crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macros ...

s are treasured and occasionally cut into

gemstone A gemstone (also called a fine gem, jewel, precious stone, semiprecious stone, or simply gem) is a piece of mineral crystal which, when cut or polished, is used to make jewellery, jewelry or other adornments. Certain Rock (geology), rocks (such ...

s. Sapphirine has also been synthesized for experimental purposes via a

hydrothermal Hydrothermal circulation in its most general sense is the circulation of hot water (Ancient Greek ὕδωρ, ''water'',Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with th ...

process.

Properties

Typical colours range from light to dark sapphire blue, bluish to brownish green, green, and bluish or greenish gray to black; less common colours include yellow, pale red, and pink to purplish pink. Sapphirine is relatively hard (7.5 on

Mohs scale The Mohs scale ( ) of mineral hardness is a qualitative ordinal scale, from 1 to 10, characterizing scratch resistance of minerals through the ability of harder material to scratch softer material. The scale was introduced in 1812 by the Ger ...

), usually transparent to translucent, with a vitreous lustre. Crystallising in the

monoclinic In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three Vector (geometric), vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in t ...

system A system is a group of interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and influenced by its open system (systems theory), environment, is described by its boundaries, str ...

, sapphirine is typically anhedral or granular in

habit A habit (or wont, as a humorous and formal term) is a routine of behavior that is repeated regularly and tends to occur subconsciously. A 1903 paper in the '' American Journal of Psychology'' defined a "habit, from the standpoint of psychology, ...

, but may also be tabular or in aggregates: Twinning is uncommon.

Fracture Fracture is the appearance of a crack or complete separation of an object or material into two or more pieces under the action of stress (mechanics), stress. The fracture of a solid usually occurs due to the development of certain displacemen ...

is subconchoidal to uneven, and there is one direction of perfect

cleavage Cleavage may refer to: Science * Cleavage (crystal), the way in which a crystal or mineral tends to split * Cleavage (embryo), the division of cells in an early embryo * Cleavage (geology), foliation of rock perpendicular to stress, a result of ...

. The

specific gravity Relative density, also called specific gravity, is a dimensionless quantity defined as the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity for solids and liquids is nea ...

of sapphirine is 3.54–3.51, and its streak is white. Sapphirine's

refractive index In optics, the refractive index (or refraction index) of an optical medium is the ratio of the apparent speed of light in the air or vacuum to the speed in the medium. The refractive index determines how much the path of light is bent, or refrac ...

(as measured by monochromatic

sodium Sodium is a chemical element; it has Symbol (chemistry), symbol Na (from Neo-Latin ) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 element, group 1 of the peri ...

light, 589.3 nm) ranges from 1.701 to 1.718 with a

birefringence Birefringence, also called double refraction, is the optical property of a material having a refractive index that depends on the polarization and propagation direction of light. These optically anisotropic materials are described as birefrin ...

of 0.006–0.007, biaxial negative. Refractive index values may correspond to colour: brownish green specimens will possess the highest values, purplish-pink specimens the lowest, and blue specimens will be intermediate between them.

Pleochroism Pleochroism is an optical phenomenon in which a substance has different colors when observed at different angles, especially with Polarization (waves), polarized light. Etymology The roots of the word are from Greek (). It was first made compou ...

may be extreme, with trichroic colours ranging from: colourless, pale yellow or red; sky to lavender blue, or bluish-green; to dark blue. There is no reaction under

ultraviolet Ultraviolet radiation, also known as simply UV, is electromagnetic radiation of wavelengths of 10–400 nanometers, shorter than that of visible light, but longer than X-rays. UV radiation is present in sunlight and constitutes about 10% of ...

light.

Formation and occurrence

While there is evidence of magmatic origin in some deposits, sapphirine is primarily a product of high grade

metamorphism Metamorphism is the transformation of existing Rock (geology), rock (the protolith) to rock with a different mineral composition or Texture (geology), texture. Metamorphism takes place at temperatures in excess of , and often also at elevated ...

in environments poor in

silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundant f ...

and rich in magnesium and aluminium. However, sapphirine occurs in a variety of rocks, including

granulite Granulites are a class of high-grade metamorphic rocks of the granulite facies that have experienced high-temperature and moderate-pressure metamorphism. They are medium to coarse–grained and mainly composed of feldspars sometimes associated ...

and

amphibolite Amphibolite () is a metamorphic rock that contains amphibole, especially hornblende and actinolite, as well as plagioclase feldspar, but with little or no quartz. It is typically dark-colored and dense, with a weakly foliated or schistose ...

facies In geology, a facies ( , ; same pronunciation and spelling in the plural) is a body of rock with distinctive characteristics. The characteristics can be any observable attribute of rocks (such as their overall appearance, composition, or con ...

, calc-silicate

skarn Skarns or tactites are coarse-grained metamorphic rocks that form by replacement of carbonate-bearing rocks during regional or contact metamorphism and metasomatism. Skarns may form by metamorphic recrystallization of impure carbonate protoliths, ...

s, and

quartzite Quartzite is a hard, non- foliated metamorphic rock that was originally pure quartz sandstone.Essentials of Geology, 3rd Edition, Stephen Marshak, p 182 Sandstone is converted into quartzite through heating and pressure usually related to tecton ...

s; it is also known from

xenolith A xenolith ("foreign rock") is a rock (geology), rock fragment (Country rock (geology), country rock) that becomes enveloped in a larger rock during the latter's development and solidification. In geology, the term ''xenolith'' is almost exclusi ...

s. Associated minerals include:

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 ...

chrysoberyl The mineral or gemstone chrysoberyl is an aluminate of beryllium with the formula Be Al2 O4. The name chrysoberyl is derived from the Greek words χρυσός ''chrysos'' and βήρυλλος ''beryllos'', meaning "a gold-white spar". Despit ...

cordierite Cordierite (mineralogy) or iolite (gemology) is a magnesium iron aluminium cyclosilicate. Iron is almost always present, and a solid solution exists between Mg-rich cordierite and Fe-rich sekaninaite with a series formula: to . A high-tempera ...

corundum Corundum is a crystalline form of aluminium oxide () typically containing traces of iron, titanium, vanadium, and chromium. It is a rock (geology), rock-forming mineral. It is a naturally transparency and translucency, transparent material, but ...

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 ...

kornerupine Kornerupine (also called ''Prismatine'') is a rare boro-silicate mineral with the chemical formula . It crystallizes in the orthorhombic – dipyramidal crystal system as brown, green, yellow to colorless slender tourmaline like prisms or in massi ...

kyanite Kyanite is a typically blue aluminosilicate mineral, found in aluminium-rich metamorphic pegmatites and sedimentary rock. It is the high pressure Polymorphism (materials science), polymorph of andalusite and sillimanite, and the presence of kyani ...

phlogopite 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 KMg3AlSi3 ...

scapolite The scapolites (, "rod", and , "stone") are a group of rock-forming silicate minerals composed of aluminium, calcium, and sodium silicate with chlorine, carbonate and sulfate. The two endmembers are meionite () and marialite (). Silvialite i ...

sillimanite Sillimanite or fibrolite is an aluminosilicate mineral with the chemical formula Al2SiO5. Sillimanite is named after the American chemist Benjamin Silliman (1779–1864). It was first described in 1824 for an occurrence in Chester, Connecticut ...

spinel Spinel () is the magnesium/aluminium member of the larger spinel group of minerals. It has the formula in the cubic crystal system. Its name comes from the Latin word , a diminutive form of ''spine,'' in reference to its pointed crystals. Prop ...

, and surinamite. Large crystals of fine clarity and colour are known from very few locales: The Central Province ( Hakurutale and Munwatte) of Sri Lanka has long been known as a source of facetable greenish blue to dark blue material, and crystals up to 30 mm or more in size have been found in

Fianarantsoa Fianarantsoa is a city (commune urbaine) in south central Madagascar, and is the capital of Haute Matsiatra Region. History It was built in the early 19th century by the Merina as the administrative capital for the newly conquered Betsileo kin ...

(

Betroka District Betroka is a district of Anosy in Madagascar. Communes The district is further divided into 20 communes: * Ambalasoa * Ambatomivary * Analamary * Andriandampy * Beapombo I * Beapombo II * Bekorobo * Benato-Toby * Betroka * Iaborotra * ...

) and

Toliara Province The Toliara Province (formerly Toliary or Tuléar) is a former province of Madagascar with an area of . It had a population of 2,229,550 (July, 2001). Its capital was Toliara. Near Toliara was the " spiny forest". Toliara Province bordered the foll ...

(Androy and Anosy regions), southern Madagascar. Sapphirine's type locality is Fiskenaesset (Fiskenaes),

Nuuk Nuuk (; , formerly ) is the capital and most populous city of Greenland, an autonomous territory in the Kingdom of Denmark. Nuuk is the seat of government and the territory's largest cultural and economic center. It is also the seat of gove ...

region, western Greenland, which is where the mineral was discovered in 1819. Other notable localities include: Western Hoggar,

Algeria Algeria, officially the People's Democratic Republic of Algeria, is a country in the Maghreb region of North Africa. It is bordered to Algeria–Tunisia border, the northeast by Tunisia; to Algeria–Libya border, the east by Libya; to Alger ...

; the Napier complex of

Enderby Land Enderby Land is a projecting landmass of Antarctica. Its shore extends from Shinnan Glacier at about to William Scoresby Bay at , approximately of the earth's longitude (planets), longitude. It was first documented in western and eastern liter ...

and the

Vestfold Hills The Vestfold Hills are rounded, rocky, coastal hills, in extent, on the north side of Sorsdal Glacier on the Ingrid Christensen Coast of Princess Elizabeth Land, Antarctica. The hills are subdivided by three west-trending peninsulas bounded by n ...

Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean (also known as the Antarctic Ocean), it contains the geographic South Pole. ...

; Delegate, New South Wales and the Strangways Range of the

Northern Territory The Northern Territory (abbreviated as NT; known formally as the Northern Territory of Australia and informally as the Territory) is an states and territories of Australia, Australian internal territory in the central and central-northern regi ...

, Australia; Wilson Lake,

Labrador Labrador () is a geographic and cultural region within the Canadian province of Newfoundland and Labrador. It is the primarily continental portion of the province and constitutes 71% of the province's area but is home to only 6% of its populatio ...

; Donghai,

Jiangsu Jiangsu is a coastal Provinces of the People's Republic of China, province in East China. It is one of the leading provinces in finance, education, technology, and tourism, with its capital in Nanjing. Jiangsu is the List of Chinese administra ...

province, China;

Kittilä Kittilä (, , ) is a municipalities of Finland, municipality of Finland and a popular holiday resort. It is located in northern Finland north of the Arctic Circle within the Lapland (Finland), Lapland Regions of Finland, region. The municipality ...

, Lapland, Finland; Ariège,

Midi-Pyrénées Midi-Pyrénées (; or ; ) is a former administrative region of France. Since 1 January 2016, it has been part of the new region of Occitania. It was the largest region of Metropolitan France by area, larger than the Netherlands or Denmark. ...

, France; Waldheim, Saxony, Germany; ,

Province of Cuneo The province of Cuneo (; ) is a province in the Piedmont region of Italy. To the west, it borders the French region of Provence-Alpes-Côte d'Azur ( departments of Alpes-Maritimes, Alpes-de-Haute-Provence and Hautes-Alpes), to the north the ...

, Piedmont, Italy;

Ulstein Ulstein may refer to: Business *Ulstein Group, a group of various marine-related industries, mainly known for shipbuilding and design *Ulstein Verft, a Norwegian shipyard Places *Ulstein Municipality, a municipality in Møre og Romsdal county, Nor ...

Møre og Romsdal Møre og Romsdal (; ) is a Counties of Norway, county in the northernmost part of Western Norway, Western Norway. It borders the counties of Trøndelag, Innlandet, and Vestland. The county administration is located in the Molde (town), town of M ...

, and

Meløy Meloy or Meløy may refer to: Places * Meløy Municipality, a municipality in Nordland county, Norway * Meløya, an island within Meløy Municipality in Nordland county, Norway * Meløy Church, a church in Meløy Municipality in Nordland county, No ...

, Nordland, Norway; the Messina District of

Limpopo Province Limpopo () is the northernmost province of South Africa. It is named after the Limpopo River, which forms the province's western and northern borders. The term Limpopo is derived from Rivombo (Livombo/Lebombo), a group of Tsonga settlers ...

and the Okiep Copper District of

Northern Cape Province The Northern Cape ( ; ; ) is the largest and most sparsely populated province of South Africa. It was created in 1994 when the Cape Province was split up. Its capital is Kimberley. It includes the Kalahari Gemsbok National Park, part of the Kga ...

, South Africa;

Falkenberg Municipality Falkenberg Municipality () is a municipality in Halland County on the Swedish west coast. The town Falkenberg is the municipal seat. The municipality was created in 1971 when the ''City of Falkenberg'' was amalgamated with six rural municipalit ...

, Halland County, Sweden; Mautia Hill in the Kongwa region of

Central Province, Tanzania Central is an adjective usually referring to being in the center of some place or (mathematical) object. Central may also refer to: Directions and generalised locations * Central Africa, a region in the centre of Africa continent, also known as ...

;

Isle of Harris Harris (, ) is the southern and more mountainous part of Lewis and Harris, the largest island in the Outer Hebrides, Scotland. Although not an island itself, Harris is often referred to in opposition to the ''Isle of Lewis'' as the Isle of Harr ...

, Outer Hebrides, Scotland; the Bani Hamid area of

Semail Ophiolite The Samail Ophiolite, also known as the Semail Ophiolite, is a large, ancient geological formation in Oman and the United Arab Emirates in the Arabian Peninsula. It is one of the world's largest and best-exposed segments of oceanic crust, made of ...

, United Arab Emirates; the

Dome Rock Mountains The Dome Rock Mountains are a mountain range in southern La Paz County, Arizona. The range borders the Colorado River on the west and the Colorado River Indian Reservation on the northwest located in the Lower Colorado River Valley. Quartzsite, ...

La Paz County, Arizona La Paz County () is the 15th County (United States), county in the U.S. state of Arizona, located in the western part of the state. As of the 2020 United States census, 2020 census, its population was 16,557, making it the List of counties ...

, Stockdale,

Riley County, Kansas Riley County is a county located in the U.S. state of Kansas. Its county seat and largest city is Manhattan. As of the 2020 census, the population was 71,959. The county was named after Bennet Riley, the 7th governor of California, and ...

;

Cortlandt, New York Cortlandt is a town in Westchester County, New York, United States, located at the northwestern edge of the county, at the eastern terminus of the Bear Mountain Bridge. As of the 2020 census, the population was 42,545. The town includes the vil ...

; and

Clay County, North Carolina Clay County is a county located in the far western part of U.S. state North Carolina. As of the 2020 census, the county population was 11,089. The county seat is Hayesville. History Early inhabitants The area that became Clay County has lo ...

; India The Eastern Ghats Mobile Belt. Sapphirine was also reported as a reaction product (together with garnet) in between Mg-Al-spinel and Ca-Tschermak-rich clinopyroxene in corundum-bearing mantle pyroxenites. Kornprobst J., Piboule M., Roden M. & Tabit A.- 1990. Corundum-bearing garnet clinopyroxenites at Beni Bousera (Morocco): original plagioclase-rich gabbros recrystallized at depth within the mantle ? J. Petrology, 31, 3, 717-745

References

{{Commons category Magnesium minerals Aluminium minerals Inosilicates Gemstones Triclinic minerals Minerals in space group 2 Minerals in space group 10