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Betafite (Betafite Group)
Current inventory:  0 gems
 

Betafite

  
Betafite is named for the the locality near Betafo District, Antananarivo Province, Madagascar where it was discovered.

Discovered in 1912;   IMA status: Valid (IMA approved 1961)

 

Chemistry

 

 

Chemical Formula:

(Ca,U)2(Ti,Nb,Ta)2O6(OH)

 

Calcium Uranium Titanium Niobium Tantalum Oxide Hydroxide

Molecular Weight:

415.12 gm

Composition:

Calcium

1.93 %

Ca

2.70 %

CaO

 

Uranium

17.20 %

U

20.67 %

UO3

 

Tantalum

21.79 %

Ta

26.61 %

Ta2O5

 

Titanium

9.23 %

Ti

15.39 %

TiO2

 

Niobium

20.14 %

Nb

28.81 %

Nb2O5

 

Aluminum

0.65 %

Al

1.23 %

Al2O3

 

Iron

1.35 %

Fe

1.92 %

Fe2O3

 

Hydrogen

0.73 %

H

6.51 %

H2O

 

Oxygen

26.98 %

O

 

 

 

 

100.00 %

 

100.00 %

= TOTAL OXIDE

 

 

Classification

   

   

Mineral Classification:

Oxides

Strunz 8th Ed. ID:

4/C.16-10

Nickel-Strunz 10th Ed. ID:

4.DH.15

 

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

Related to:

Pyrochlore Supergroup. Pyrochlore Group. Betafite Subgroup. The calcium analogue of the other members of the Betafite Subgroup.

Members of Supergroup:

Pyrochlore Supergroup: Betafite Group, Elsmoreite Group, Microlite Group, Pyrochlore Group, Romérite Group

Members of Group:

Pyrochlore Group: Fluorcalciopyrochlore, Fluorkenopyrochlore, Fluornatropyrochlore, Fluorstrontiopyrochlore, Hydropyrochlore, Hydroxycalciopyrochlore, Kenoplumbopyrochlore, Oxycalciopyrochlore, Oxynatropyrochlore, Oxyplumbopyrochlore, Oxyyttropyrochlore-(Y)

Members of Subgroup:

Betafite Subgroup: Oxycalciobetafite, Oxyuranobetafite

Varieties:

Aluminian Betafite, Barian Betafite, Tangenite

Synonyms:

Blomstrandite, Mendeleyevite, Mendelyeevite, Samiresite, Tantalbetafite, Titanbetafite

 

 

Crystal Data

   

   

Crystallography:

Isometric - Hexoctahedral

Crystal Habit:

Crystals commonly octahedra modified by [110], [100], [113], [233], and [230]; some crystals elongated k [001] or [111]; to 15 cm.

Twinning:

None

 

 

Physical Properties

   

 

Cleavage:

None observed

Fracture:

Conchoidal to Irregular/Uneven

Tenacity:

Brittle

Moh's Hardness:

3.0 - 5.5

Density:

3.70 - 4.90 (g/cm3)

Luminescence:

Radioactive

Radioactivity:

Very Strong; GRapi = 1,310,418.25 (Gamma Ray American Petroleum Institute Units)

Health Warning:

Contains Uranium - always wash hands after handling. Avoid inhaling dust when handling or breaking. Never lick or ingest. Avoid prolonged exposure in proximity of the body. Store away from inhabited areas.

 

 

Optical Properties

   

   

Color:

Red; Greenish Brown, dark Brown to Black when metamict, commonly superficially altered Yellow; almost Colorless in transmitted light.

Transparency:

Translucent to Opaque

Luster:

Waxy, Greasy to Adamantine, Semimetallic

Refractive Index:

1.910 - 2.197  Isotropic

Birefringence:

0.000  (Isotropic)

Dispersion:

None

Pleochroism:

None

Reflectivity:

(400) 13.5, (420) 13.2, (440) 13.0, (460) 12.8, (480) 12.6, (500) 12.4, (520) 12.3, (540) 12.2, (560) 12.0, (580) 11.9, (600) 11.7, (620) 11.6, (640) 11.6, (660) 11.6, (680) 11.5, (700) 11.5

 

 

Occurances

   

   

Geological Setting:

Typically a primary mineral in granite pegmatites; rare in carbonatites.

Common Associations:

Allanite, Beryl, Biotite, Magnetite, Microcline, Quartz, Thorite, Titanite, Zircon

Common Impurities:

Al, Fe, K, Mg, Pb, REE, Sn, Ta, Th, W, Zr

Type Locality:

Ambolotara, Betafo Commune, Betafo District, Vakinankaratra Region (Betafo - Antsirabé region), Antananarivo Province, Madagascar

Year Discovered:

1912 (IMA approved 1961)

View mineral photos:

Betafite Mineral Photos and Locations

 

 

More Information

   

   

 

Mindat.org
Webmineral.com

 

 


Betafite is a very rare gem that is highly radioactive. It is mainly for collectors of very unusual gems or radioactive gems. It is one of the few uranium bearing minerals to form as well shaped crystals. Betafite is one of several so called Rare Earth Oxides. Other rare earth oxides such as Aeschynite-(Y),
Euxenite-(Y), Fergusonite-(Ce) and Samarskite-(Y) have similar properties but do not form as well shaped crystals like those typical of Betafite. Betafite was discovered in 1912 at Ambolotara, Betafo District, Madagascar. It is a member of the Pyrochlore Group that typically occurs as a primary mineral in granite pegmatites, rarely in carbonates.

Sources of Betafite: In Madagascar, large crystals at a number of localities, including: from Ambolotara, west of Betafo; Ambatolampikely; Ambatofotsy; Ambatomboahangy; Ambalahazo; Tomboarivo; and Antanifotsy. In Norway, at Höysjåen, near Kragerø; Landsverk quarry, near Evje; and Ljosland. From Slyudyanka, near Lake Baikal, Siberia, Russia. In the Silver Crater mine, Wilberforce, Ontario, and elsewhere in Canada. In the USA, in the Brown Derby pegmatite, Gunnison County, Colorado; in the Pidlite pegmatite, Mora County, New Mexico; and from the Cady Mountains, San Bernardino County, California.

Betafite is a highly radioactive mineral and should be stored away from other minerals and gems that might be damaged by radioactivity. Human contact and exposure to Thorite mineral specimens or gems should be limited!
 

  
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