Neptunite

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Neptunite
Neptunite, benitoite, joaquinite-(Ce) sur natrolite et serpentine (USA) 2.jpg
Neptunite crystals
General
Category Phyllosilicate
Formula
(repeating unit)
KNa2Li(Fe2+,Mn2+)2Ti2Si8O24
IMA symbol Npt [1]
Strunz classification 9.EH.05
Dana classification70.04.01.01
Crystal system Monoclinic
Crystal class Domatic (m)
(same H-M symbol)
Space group Cc
Unit cell a = 16.427(2), b = 12.478(2)
c = 9.975(1) Å; β = 115.56(1)°; Z = 4
Identification
ColorBlack; deep red-brown in thin fragments
Crystal habit Prismatic or tabular
Twinning Interpenetrant on {301}
Cleavage {110} good
Fracture Conchoidal
Tenacity Brittle
Mohs scale hardness5–6
Luster Vitreous
Streak Brown to red brown
Diaphaneity Nearly opaque
Specific gravity 3.19–3.23
Optical propertiesBiaxial (+)
Refractive index nα = 1.69–1.6908,
nβ = 1.6927–1.7,
nγ = 1.7194–1.736
Birefringence 0.0294–0.0452
Pleochroism x = yellow-orange, y = orange, z = deep red
2V angle 36° to 49°
Other characteristicsPiezoelectric
References [2] [3] [4]

Neptunite is a silicate mineral with the formula K Na 2 Li(Fe 2+, Mn 2+)2 Ti 2 Si 8 O 24. With increasing manganese it forms a series with mangan-neptunite. Watatsumiite is the variety with vanadium replacing the titanium in the formula.

It was first described in 1893 for an occurrence in the Narssârssuk pegmatite of West Greenland. [3] It is also found within natrolite veins in glaucophane schist within serpentinite in San Benito County, California, US. It also occurs in Mont Saint-Hilaire, Quebec [5] and in the Kola Peninsula of Russia. [2]

The mineral is named for Neptune, Roman god of the sea because of its association with aegirine from Àgir , the Scandinavian sea-god. [3]

The Gemological Institute of America (GIA) identified an 11.78-carat faceted specimen as neptunite based on Raman spectroscopy. [6]

Related Research Articles

<span class="mw-page-title-main">Tugtupite</span>

Tugtupite is a beryllium aluminium tectosilicate. It also contains sodium and chlorine and has the formula Na4AlBeSi4O12Cl. Tugtupite is a member of the silica-deficient feldspathoid mineral group. It occurs in high alkali intrusive igneous rocks.

<span class="mw-page-title-main">Natrolite</span> Zeolite mineral

Natrolite is a tectosilicate mineral species belonging to the zeolite group. It is a hydrated sodium and aluminium silicate with the formula Na2Al2Si3O10·2H2O. The type locality is Hohentwiel, Hegau, Germany.

<span class="mw-page-title-main">Aegirine</span> Member of the clinopyroxene group of inosilicate mineral

Aegirine is a member of the clinopyroxene group of inosilicate minerals. It is the sodium endmember of the aegirine–augite series. It has the chemical formula NaFeSi2O6, in which the iron is present as the ion Fe3+. In the aegirine–augite series, the sodium is variably replaced by calcium with iron(II) and magnesium replacing the iron(III) to balance the charge. Aluminum also substitutes for the iron(III). Acmite is a fibrous green-colored variety.

<span class="mw-page-title-main">Abenakiite-(Ce)</span> Cyclosilicate mineral

Abenakiite-(Ce) is a mineral of sodium, cerium, neodymium, lanthanum, praseodymium, thorium, samarium, oxygen, sulfur, carbon, phosphorus, and silicon with a chemical formula Na26Ce6(SiO3)6(PO4)6(CO3)6(S4+O2)O. The silicate groups may be given as the cyclic Si6O18 grouping. The mineral is named after the Abenaki, an Algonquian Indian tribe of New England. Its Mohs scale rating is 4 to 5.

<span class="mw-page-title-main">Sugilite</span> Violet-colored crystal

Sugilite ( SOO-gə-lyte, -⁠jee-) is a relatively rare pink to purple cyclosilicate mineral with the complex chemical formula KNa2(Fe, Mn, Al)2Li3Si12O30. Sugilite crystallizes in the hexagonal system with prismatic crystals. The crystals are rarely found and the form is usually massive. It has a Mohs hardness of 5.5–6.5 and a specific gravity of 2.75–2.80. It is mostly translucent. Sugilite was first described in 1944 by the Japanese petrologist Ken-ichi Sugi (1901–1948) for an occurrence on Iwagi Islet, Japan, where it is found in an aegirine syenite intrusive stock. It is found in a similar environment at Mont Saint-Hilaire, Quebec, Canada. In the Wessels mine in Northern Cape Province of South Africa, sugilite is mined from a strata-bound manganese deposit. It is also reported from Liguria and Tuscany, Italy; New South Wales, Australia and Madhya Pradesh, India.

<span class="mw-page-title-main">Steacyite</span>

Steacyite is a complex silicate mineral containing thorium and uranium; formula Kvariable(Ca,Na)2(Th,U)Si8O20. It forms small brown or yellow green crystals, often cruciform twinned crystals. It is radioactive. It was discovered at Mont-Saint-Hilaire, Quebec in 1982 and is named after Harold Robert Steacy (1923–2012), mineralogist.

Zircophyllite is a complex mineral, formula (K,Na)3(Mn,Fe)2+7(Zr,Ti,Nb)2Si8O24(OH,F)7. It crystallizes in the triclinic – pinacoidal crystal class as dark brown to black micaceous plates. It has perfect 001 cleavage, a Mohs hardness of 4 to 4.5 and a specific gravity of 3.34. Its indices of refraction are nα=1.708 nβ=1.738 nγ=1.747 and it has a 2V optical angle of 62°.

<span class="mw-page-title-main">Mckelveyite-(Y)</span>

Mckelveyite-(Y) is a hydrated sodium, barium, yttrium, and uranium–containing carbonate mineral, with the chemical formula Ba3Na(Ca,U)Y(CO3)6·3H2O.

<span class="mw-page-title-main">Siderophyllite</span>

Siderophyllite is a rare member of the mica group of silicate minerals with formula KFe2+2Al(Al2Si2)O10(F,OH)2.

<span class="mw-page-title-main">Carletonite</span>

Carletonite is a rare silicate mineral with formula KNa4Ca4(CO3)4Si8O18(F,OH)·(H2O).

<span class="mw-page-title-main">Stillwellite-(Ce)</span>

Stillwellite-(Ce) is a rare-earth boro-silicate mineral with chemical formula (Ce,La,Ca)BSiO5.

<span class="mw-page-title-main">Serandite</span> Mineral

Serandite is a mineral 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.

<span class="mw-page-title-main">Narsarsukite</span>

Narsarsukite is a rare silicate mineral with either the chemical formula Na2(Ti,Fe3+)Si4(O,F)11 or Na4(Ti,Fe)4[Si8O20](O,OH,F)4.

<span class="mw-page-title-main">Ferrokentbrooksite</span> Mineral of the eudialyte group

Ferrokentbrooksite is a moderately rare mineral of the eudialyte group, with formula Na15Ca6(Fe,Mn)3Zr3NbSi25O73(O,OH,H2O)3(Cl,F,OH)2. The original formula was extended form to show the presence of cyclic silicate groups and presence of silicon at the M4 site, according to the nomenclature of eudialyte group. As suggested by its name, it is the (ferrous) iron analogue of kentbrooksite. When compared to the latter, it is also chlorine-dominant instead of being fluorine-dominant. The original (holotype) material is also relatively enriched in rare earth elements, including cerium and yttrium.

Johnsenite-(Ce) is a very rare mineral of the eudialyte group, with the chemical formula Na12(Ce,La,Sr,Ca,[ ])3Ca6Mn3Zr3WSi(Si9O27)2(Si3O9)2(CO3)O(OH,Cl)2. The original formula was extended to show the presence of both the cyclic silicate groups and silicon at the M4 site, according to the nomenclature of the eudialyte group. It is the third eudialyte-group mineral with essential tungsten, and second with essential rare earth elements. In fact, some niobium substitutes for tungsten in johnsenite-(Ce). Other characteristic feature is the presence of essential carbonate group, shared with carbokentbrooksite, golyshevite, mogovidite and zirsilite-(Ce).

<span class="mw-page-title-main">Khomyakovite</span> Mineral of the eudialyte group

Khomyakovite is an exceedingly rare mineral of the eudialyte group, with formula Na12Sr3Ca6Fe3Zr3W(Si25O73)(O,OH,H2O)3(OH,Cl)2. The original formula was extended to show the presence of both the cyclic silicate groups and M4-site silicon, according to the nomenclature of the eudialyte group. Some niobium substitutes for tungsten in khomyakovite. Khomyakovite is an iron-analogue of manganokhomyakovite, the second mineral being a bit more common. The two minerals are the only group representatives, beside taseqite, with species-defining strontium, although many other members display strontium diadochy. Khomyakovite is the third eudialyte-group mineral with essential tungsten.

<span class="mw-page-title-main">Manganokhomyakovite</span>

Manganokhomyakovite is a very rare mineral of the eudialyte group, with the chemical formula Na12Sr3Ca6Mn3Zr3WSi(Si9O27)2(Si3O9)2O(O,OH,H2O)3(OH,Cl)2. This formula is in extended form, to show the presence of cyclic silicate groups and domination of silicon at the M4 site, basing on the nomenclature of the eudialyte group. Some niobium substitutes for tungsten in khomyakovite. As suggested by its name, manganokhomyakovite is a manganese-analogue of khomyakovite, the latter being more rare. The two minerals are the only group representatives, beside taseqite, with species-defining strontium, although many other members display strontium diadochy. Manganokhomyakovite is the third eudialyte-group mineral with essential tungsten.

Oneillite is a rare mineral of the eudialyte group with the chemical formula Na15Ca3Mn3Fe2+3Zr3NbSiO(Si3O9)2(Si9O27)2(O,OH,H2O)3(OH,Cl)2. The formula is based on the original one but extended to show the presence of cyclic silicate groups and domination of Si at the M4 site. The mineral has lowered symmetry (space group R3, instead of more specific for the group R3m one) due to Ca-Mn ordering. Similar feature is displayed by some other eudialyte-group members: aqualite, labyrinthite, raslakite, and voronkovite. Oneillite is strongly enriched in rare earth elements (REE, mainly cerium), but REE do not dominate any of its sites.

Charleshatchettite is a very rare, complex, niobium oxide mineral with the formula CaNb4O10(OH)2•8H2O. It was discovered in the mineral-rich site Mont Saint-Hilaire, Montérégie, Québec, Canada.

<span class="mw-page-title-main">Lizardite</span> Magnesium phyllosilicate mineral of the serpentine group

Lizardite is a mineral from the serpentine subgroup with formula Mg3(Si2O5)(OH)4, and the most common type of mineral in the subgroup. It is also a member of the kaolinite-serpentine group.

References

  1. Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi: 10.1180/mgm.2021.43 . S2CID   235729616.
  2. 1 2 Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C. (2005). "Neptunite" (PDF). Handbook of Mineralogy. Mineral Data Publishing. Retrieved 14 March 2022.
  3. 1 2 3 Neptunite, Mindat.org
  4. Webmineral
  5. Normand, Charles; Tarassoff, Peter (2006). Mineralogy and geology of the Poudrette quarry, Mont SaintHilaire, Quebec (PDF). Mineralogical Association of Canada. Retrieved 12 March 2022.
  6. Cooper, Amy; Allen, Tara (Summer 2013). "Rare faceted neptunite". Gems & Gemology. Gemological Institute of America. 49 (2). Retrieved April 18, 2019.