Eudialyte, whose name derives from the Greek phrase , , meaning "well decomposable", is a somewhat rare, nine member ring

cyclosilicate Silicate minerals are rock-forming minerals made up of silicate groups. They are the largest and most important class of minerals and make up approximately 90 percent of Earth's crust. In mineralogy, silica (silicon dioxide, ) is usually consi ...

mineral, which forms in

alkaline In chemistry, an alkali (; from ar, القلوي, al-qaly, lit=ashes of the saltwort) is a basic, ionic salt of an alkali metal or an alkaline earth metal. An alkali can also be defined as a base that dissolves in water. A solution of ...

igneous rocks, such as nepheline

syenite Syenite is a coarse-grained intrusive igneous rock with a general composition similar to that of granite, but deficient in quartz, which, if present at all, occurs in relatively small concentrations (< 5%). Some syenites contain larger prop ...

s. Its name alludes to its ready solubility in acid. Eudialyte was first described in 1819 for an occurrence in nepheline syenite of the

Ilimaussaq intrusive complex The Ilimaussaq intrusive complex is a large alkalic layered intrusion located on the southwest coast of Greenland. It is Mesoproterozoic in age, about 1.16 Ga. It is the type locality of agpaitic nepheline syenite and hosts a variety of unusual ...

of southwest Greenland.

Uses of eudialyte

Eudialyte is used as a minor ore of

zirconium Zirconium is a chemical element with the symbol Zr and atomic number 40. The name ''zirconium'' is taken from the name of the mineral zircon, the most important source of zirconium. The word is related to Persian '' zargun'' (zircon; ''zar-gun'', ...

. Another use of eudialyte is as a minor gemstone, but this use is limited by its rarity, which is compounded by its poor crystal habit. These factors make eudialyte of primary interest as a collector's mineral. Eudialyte typically has a significant content of U, Pb, Nb, Ta, Zr, Hf, and

rare earth elements The rare-earth elements (REE), also called the rare-earth metals or (in context) rare-earth oxides or sometimes the lanthanides (yttrium and scandium are usually included as rare earths), are a set of 17 nearly-indistinguishable lustrous silve ...

(REE). Because of this, geoscientists use eudialyte as a geochronometer to date and investigate the genesis of the host rocks.

Associated minerals

Eudialyte is found associated with other alkalic igneous minerals, in addition to some minerals common to most igneous material in general. Associate minerals include:

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 durin ...

, nepheline,

aegirine Aegirine is a member of the clinopyroxene 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-augite ...

lamprophyllite Lamprophyllite (named for its lustrous cleavage) is a rare, but widespread mineral Ti-silicate mineral usually found in intrusive agpasitic igneous rocks. Yellow, reddish brown, Vitreous, Pearly. Lamprophyllite formula is (Sr,Ba,K,Na)2Na(Na,Fe, ...

lorenzenite Lorenzenite is a rare sodium titanium silicate mineral with the formula Na2 Ti2 Si2 O9 It is an orthorhombic mineral, variously found as colorless, grey, pinkish, or brown crystals. It was first identified in 1897 in rock samples from Narsarsuk ...

catapleiite Catapleiite (•2) is a dimorph of Gaidonnayite rarely found by itself. Its name derives from the Greek words “κατα” (kata) and “πλειον” (pleion) meaning “with more” as it is mostly accompanied by a number of rare mineral ...

, murmanite,

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 ...

, sodalite,

aenigmatite Aenigmatite, also known as ''Cossyrite'' after Cossyra, the ancient name of Pantelleria, is a sodium, iron, titanium inosilicate mineral. The chemical formula is Na2Fe2+5TiSi6O20 and its structure consists of single tetrahedral chains with a repe ...

, rinkite, låvenite,

titanite Titanite, or sphene (from the Greek ''sphenos'' (σφηνώ), meaning wedge), 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 in ...

and titanian

magnetite Magnetite is a mineral and one of the main iron ores, with the chemical formula Fe2+Fe3+2O4. It is one of the oxides of iron, and is ferrimagnetic; it is attracted to a magnet and can be magnetized to become a permanent magnet itself. With the ...

Alternative names

Alternative names of eudialyte include: almandine spar, eudalite, Saami blood. Eucolite is the name of an optically negative variety, more accurately the group member: ferrokentbrooksite.Eucolite on Mindat
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Notes for identification

Eudialyte's rarity makes locality useful in its identification. Prominent localities of eudialyte include

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 ...

in Canada,

Kola Peninsula The Kola Peninsula (russian: Кольский полуостров, Kolsky poluostrov; sjd, Куэлнэгк нёа̄ррк) is a peninsula in the extreme northwest of Russia, and one of the largest peninsulas of Europe. Constituting the bulk ...

Russia Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-eight ...

and

Poços de Caldas Poços de Caldas is a municipality in the south of Minas Gerais state, Brazil, in the microregion of the same name. Its estimated population in 2020 was 168,641 inhabitants. The city is known for its hot springs. History Poços was founded in 1 ...

in Brazil, but it is also found in Greenland, Norway, and

Arkansas Arkansas ( ) is a landlocked state in the South Central United States. It is bordered by Missouri to the north, Tennessee and Mississippi to the east, Louisiana to the south, and Texas and Oklahoma to the west. Its name is from the Osage la ...

. The lack of crystal habit, associated with color, is also useful for identification, as are associated minerals. A pink-red mineral with no good crystals associated with other alkaline igneous material, especially nepheline and aegirine, is a good indication a specimen is eudialyte.

Eudialyte group

Microchemical (by electron microprobe) and structural analyses of different eudialyte (and related) samples have revealed the presence of many new eudialyte-like minerals. These minerals are structurally and chemically related and joined into the eudialyte group. The group includes Zr-, OH-, Cl-, F-, CO₃- and possibly also SO₄-bearing silicates of Na, K, H₃O, Ca, Sr, REEs, Mn, Fe, Nb and W. Electron vacancies can be present in their structure, too.

References