Euxenite-(Y)
Current inventory:  0 gems
 

  
Euxenite is named from the Greek for "friendly to strangers, or hospitable," in allusion to the wide variety of rare elements that it contains.

Discovered in 1870;   IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

(Y,Ca,Ce,U,Th)(Nb,Ta,Ti)₂O₆

Yttrium Calcium Cerium Niobium Tantalum Titanium Oxide

Molecular Weight:

392.28 gm

Composition:

Calcium

2.04 %

Ca

2.86 %

CaO

Cerium

3.57 %

Ce

4.18 %

Ce₂O₃

Yttrium

15.86 %

Y

20.15 %

Y₂O₃

Tantalum

18.45 %

Ta

22.53 %

Ta₂O₅

Titanium

2.44 %

Ti

4.07 %

TiO₂

Niobium

33.16 %

Nb

47.43 %

Nb₂O₅

Oxygen

24.47 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Oxides

Strunz 8th Ed. ID:

4/D.14-20

Nickel-Strunz 10th Ed. ID:

4.DG.05

4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
D : Metal: Oxygen = 1:2 and similar
G : With large (+- medium-sized) cations; chains of edge-sharing octahedra

Related to:

Polycrase Group

Varieties:

None

Synonyms:

Euxenite, Guimaraesite (of Gagarin & Cuomo), Lyndochite

Crystal Data

Crystallography:

Orthorhombic - Dipyramidal  (may be metamict - a mineral originally crystalline, eventually amorphous due to radiation damage)

Crystal Habit:

As stout prismatic crystals, to 10 cm, may be flattened || [100] or [010]; commonly in parallel, subparallel, or radiating aggregates; compact massive.

Twinning:

Common on {201}; rare on {101} or {013}

Physical Properties

Cleavage:

None

Fracture:

Conchoidal to Sub-Conchoidal

Tenacity:

Brittle

Moh's Hardness:

5.5 - 6.5

Density:

5.30 - 5.90 (g/cm³)

Luminescence:

None

Radioactivity:

Mild; GRapi = 3,420.62 (Gamma Ray American Petroleum Institute Units)

Optical Properties

Color:

Black, Brownish Black, Greenish Black; Brown to Yellow-Brown in transmitted light

Transparency:

Opaque, Translucent on thin edges

Luster:

Vitreous to Sub-Metallic, Waxy to Resinous on fractures

Refractive Index:

2.06 - 2.24  Isotropic; R₁–R₂: (470) 13.7–15.6, (546) 13.0–15.6, (589) 12.5–15.0, (650) 12.4–15.0

Birefringence:

0.000  Isotropic

Pleochroism:

None

Occurances

Geological Setting:

From granite pegmatites; as a component of detrital black sands

Common Associations:

Aeschynite-(Y), Albite, Allanite, Betafite, Beryl, Biotite, Columbite, Gadolinite, Garnet, Ilmenite, Magnetite, Microcline, Monazite, Muscovite, Thorite, Uraninite, Xenotime, Zircon

Type Locality:

Jølster, Sunnfjord, Sogn og Fjordane, Norway

Year Discovered:

1870

View mineral photos:

Euxenite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Euxenite-(Y) is a very rare radioactive mineral that belongs to the Polycrase Group of minerals that includes Euxenite-(Y), Polycrase-(Y) and Yttrocrasite-(Y). Because of the rare earth metals in its structure, Euxenite is one of several minerals called "Rare Earth Oxides". Other rare earth oxides such as Aeschynite, Fergusonite and Samarskite have very similar properties to Euxenite and are often associated with each other. Faceted Euxenite gems are extremely rare and really only faceted as a collector's oddity.

Euxenite is a mildly radioactive mineral and should be stored away from other gems and minerals that are subject to damage from radioactivity and of course human exposure should be limited.

Euxenite may be metamict due to its mild radioactivity. Metamictization is a natural, gradual process of the complete destruction of the internal crystal structure of a mineral due to radiation present in the mineral or from nearby external radiation. Metamictization eventually leaves the mineral amorphous or without any internal crystal structure. Once this process is complete the mineral is desctibed as metamict.

There are numerous Euxenite localities worldwide. In Norway, from Jölster, Söndfjord; at Alve, on Tromö Island; on Hidra (Hitterö) Island, near Flekkefjord; at many other places between Tvedestrand and Arendal, and in Iveland and Evje Parishes, Sätersdal. In Sweden, in the Ruoutevare Fe–Ti deposit, near Kvikkjokk, Norrbotten; at Ytterby, on Resarö Island, near Vaxholm; and elsewhere. From Huntila, Pitkäranta district, Lake Ladoga, Karelia, Russia. In Madagascar, large crystals from Vohimasina; Ambatofotsikely; Ankazobe, near Ambohitantely; Ambolotara; Ranomafana; and elsewhere. In Brazil, from Santa Clara, Pomba, and Espirito Santo, Minas Gerais. In Canada, from Lyndoch, Sabine, and Mattawan Townships, and elsewhere in Ontario; also in Quebec. In the USA, from the Rutherford pegmatite, Amelia County, the Nanco pegmatite, Bedford County, and others in Virginia; from Morton, Delaware County, Pennsylvania; at Encampment, Carbon County, Wyoming; from Guffey, Park County, near Bergen Park, Jefferson County, and the Colorado feldspar pegmatite, Fremont County, Colorado.

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