Serandite is a

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 ...

with formula Na(Mn²⁺,Ca)₂Si₃O₈(OH). The mineral was discovered in Guinea in 1931 and named for J. M. Sérand. Serandite is generally red, brown, black or colorless. The correct name lacks an accent.

Description

Serandite is transparent to translucent and is normally salmon-pink, light pink, rose-red, orange, brown, black, or colorless; in

thin section In optical mineralogy and petrography, a thin section (or petrographic thin section) is a thin slice of a rock or mineral sample, prepared in a laboratory, for use with a polarizing petrographic microscope, electron microscope and electron ...

, it is colorless. Octahedrally bonded Mn(II) is the primary contributor to the mineral's pink colors.Manning, p. 357. Crystals of the mineral can be prismatic to acicular and elongated along 10 bladed, blocky, or tabular and flattened on , occur as a radiating aggregate, or have massive

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.

. Sérandite is a member of the wollastonite group and is the manganese analogue of

pectolite Pectolite is a white to gray mineral, Na Ca2 Si3 O8(O H), sodium calcium hydroxide inosilicate. It crystallizes in the triclinic system typically occurring in radiated or fibrous crystalline masses. It has a Mohs hardness of 4.5 to 5 and a specif ...

. It is sometimes used as a gemstone.Gemstones of North America - Volume 3 - Page 417 John Sinkankas - 1959

History

Serandite was discovered on Rouma Island, part of the Los Islands in Guinea. The mineral was described by À. Lacroix in the journal '' Comptes rendus hebdomadaires des séances de l'Académie des Sciences''.Lacroix, p. 189. He named it ''sérandite'' in honor of J.M. Sérand, a mineral collector who helped in the collection of the mineral.

Occurrence and distribution

Serandite has been found in Australia, Brazil, Canada, Guinea, Italy, Japan, Namibia, Norway, Russia, South Africa, and the United States. The

type material In biology, a type is a particular specimen (or in some cases a group of specimens) of an organism to which the scientific name of that organism is formally attached. In other words, a type is an example that serves to anchor or centralizes t ...

is held at the

National Museum of Natural History The National Museum of Natural History is a natural history museum administered by the Smithsonian Institution, located on the National Mall in Washington, D.C., United States. It has free admission and is open 364 days a year. In 2021, with 7 ...

in Washington, D.C. At

Mont Saint-Hilaire Mont Saint-Hilaire (English: Mount Saint-Hilaire; abe, Wigwômadenizibo; see for other names) is an isolated hill, high, in the Montérégie region of southern Quebec. It is about thirty kilometres east of Montreal, and immediately east of the ...

, Quebec, serandite occurs in sodalite

xenolith A xenolith ("foreign rock") is a rock fragment ( country rock) that becomes enveloped in a larger rock during the latter's development and solidification. In geology, the term ''xenolith'' is almost exclusively used to describe inclusions in ig ...

s and pegmatites cutting syenites within an intrusive alkalic

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 ch ...

- syenite complex. In Point of Rocks, New Mexico, it occurs in

vug A vug, vugh, or vugg ( ) is a small- to medium-sized cavity inside rock. It may be formed through a variety of processes. Most commonly, cracks and fissures opened by tectonic activity (folding and faulting) are partially filled by quartz, ...

s in phonolite. At the Tumannoe deposit in Russia, serandite occurs in a manganese rich deposit associated with

volcanic rock Volcanic rock (often shortened to volcanics in scientific contexts) is a rock formed from lava erupted from a volcano. In other words, it differs from other igneous rock by being of volcanic origin. Like all rock types, the concept of volcanic ...

s and terrigenous (non-marine)

sediment Sediment is a naturally occurring material that is broken down by processes of weathering and erosion, and is subsequently transported by the action of wind, water, or ice or by the force of gravity acting on the particles. For example, sa ...

s which has been altered by

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

. Serandite has been found in association with

aegirine Aegirine is a member of the clino pyroxene group of inosilicate minerals. Aegirine is the sodium endmember of the aegirine-augite series. Aegirine has the chemical formula Na Fe Si2 O6 in which the iron is present as Fe3+. In the aegirine-augit ...

analcime Analcime (; ) or analcite is a white, gray, or colorless tectosilicate mineral. Analcime consists of hydrated sodium aluminium silicate in cubic crystalline form. Its chemical formula is Na Al Si2 O6· H2O. Minor amounts of potassium and calci ...

arfvedsonite Arfvedsonite () is a sodium amphibole mineral with composition: aNa2] Fe2+)4Fe3+(OH)2, Si8O22]. It crystallizes in the monoclinic prismatic crystal system and typically occurs as greenish black to bluish grey fibrous to radiating or stellate pr ...

astrophyllite Astrophyllite is a very rare, brown to golden-yellow hydrous potassium iron titanium silicate mineral. Belonging to the astrophyllite group, astrophyllite may be classed either as an inosilicate, phyllosilicate, or an intermediate between th ...

eudialyte Eudialyte, whose name derives from the Greek phrase , , meaning "well decomposable", is a somewhat rare, nine member ring cyclosilicate mineral, which forms in alkaline igneous rocks, such as nepheline syenites. Its name alludes to its ready ...

fluorite Fluorite (also called fluorspar) is the mineral form of calcium fluoride, CaF2. It belongs to the halide minerals. It crystallizes in isometric cubic habit, although octahedral and more complex isometric forms are not uncommon. The Mohs sca ...

, leucophanite, mangan-neptunite,

microcline Microcline (KAlSi3O8) is an important igneous rock-forming tectosilicate mineral. It is a potassium-rich alkali feldspar. Microcline typically contains minor amounts of sodium. It is common in granite and pegmatites. Microcline forms during slo ...

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 pegmatite ...

sodalite Sodalite ( ) is a tectosilicate mineral with the formula , with royal blue varieties widely used as an ornamental gemstone. Although massive sodalite samples are opaque, crystals are usually transparent to translucent. Sodalite is a member of t ...

, and villiaumite.

References

Bibliography

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External links