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Gadolinite-(Y)

Discovered in 1800;   IMA status: Valid (pre-IMA; Grandfathered).

Chemistry

Chemical Formula:

Y₂Fe²⁺Be₂(Si₂O₁₀)

Yttrium Iron Beryllium Silicate

Molecular Weight:

614.71 gm

Composition:

Yttrium

38.01 %

Y

48.27 %

Y₂O₃

Beryllium

3.85 %

Be

10.59 %

BeO

Iron

11.94 %

Fe

15.36 %

FeO

Silicon

12.04 %

Si

25.69 %

SiO₂

Oxygen

34.20 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/B.29-50

Nickel-Strunz 10th Ed. ID:

9.AJ.20

9 : SILICATES (Germanates)
A : Neosilicates
J : Nesosilicates with BO₃ triangles and/or B[4], Be[4] tetrahedra, cornersharing with SiO₄
20 : Datolite/Gadolinite group

Related to:

Datolite Group (Homilite series); Gadolinite Subgroup > Gadolinite Group > Gadolinite Supergroup

Members of Group:

Datolite Group: Bakerite, Gadolinite-(Ce), Gadolinite-(Y), Homilite, Minasgeraisite-(Y)

Members of Group:

Gadolinite Subgroup: Calcybeborosilite-(Y), Gadolinite-(Ce), Gadolinite-(Nd), Gadolinite-(Y), Hingganite-(Ce), Hingganite-(Nd), Hingganite-(Y), Hingganite-(Yb), Minasgeraisite-(Y) 

Varieties:

Calcioadolinite-(Y)

Synonyms:

Calciogadolinite, Ytterbite, Yttrite

Crystal Data

Crystallography:

Monoclinic - Prismatic (often metamict - a mineral originally crystalline, eventually amorphous due to radiation damage)

Crystal Habit:

Crystals rough; typically prismatic, terminated, and many other forms, to 25 cm; commonly massive.

Twinning:

None

Physical Properties

Cleavage:

None

Fracture:

Conchoidal or Splintery

Tenacity:

Brittle

Moh's Hardness:

6.5 - 7.0

Density:

4.36 - 4.77 (g/cm³) (when non-metamict)

Luminescence:

None

Radioactivity:

(Y): Not Radioactive

(Ce): Weak; GRapi = 44,145.76 (Gamma Ray American Petroleum Institute Units)

Optical Properties

Color:

Black, greenish black, brown; grass-green to olive-green in thin fragments.

Transparency:

Transparent to Opaque

Luster:

Vitreous to Greasy

Refractive Index:

1.770 - 1.820  Biaxial ( + ), Isotropic when metamict

Birefringence:

0.0500

Dispersion:

Strong; r < v

Pleochroism:

None

Occurances

Geological Setting:

In granite and alkalic granite pegmatites.

Common Associations:

Quartz, Anatase, Fluorite, Microcline, Biotite, Tengerite-(Y), Calcioancylite-(Nd), Orthoclase, Synchysite-(Y), Albite

Common Impurities:

None

Type Locality:

Ytterby, Resarö, Vaxholm, Stockholm, Sweden

Year Discovered:

1800

View mineral photos:

Gadolinite-(Y) Mineral Photos and Locations

Unusual Gem Categories

Metamict Gems

More Information

Mindat.org  (Gadolinite-(Y)
Webmineral.com  (Gadolinite-(Y)

Gadolinite is a relatively rare mineral that is usually black and is often weakly radioactive due to minor Cerium (Ce), Uranium (U) or Thorium (Th) content. Because Gadolinite is a weakly radioactive mineral it should be stored away from other gems and minerals that are subject to damage from radioactivity and of course human exposure should be limited.

Gadolinite may also be metamict due to its weak 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 described as metamict.

Gadolinite was named in honor of Finnish chemist, physicist, and mineralogist, Johan Gadolin (1760-1852), who discovered the element Yttrium. The (Y) designation is added to Gadolinite for its Yttrium content. Yttrium was the first Rare Earth Element (REE) discovered. The element gadolinium was also named after Johan Gadolin in 1880.

Godolinite is available from several localities worldwide: Ytterby, Sweden; ResarÄo Island and elsewhere in Norway; Val Bedretto, Ticino, Switzerland; Badgastein, Salzburg, Austria; Loughborough Township, Frontenac County, Ontario, Canada. In the USA, in the Clear Creek pegmatite, Llano County, Texas; near Hackberry, Mohave County, Arizona; near Lake George, Park County, Colorado.

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