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Ankangite (inclusions in Quartz)

Discovered in 1986; IMA status: Not Valid (IMA Discredited 2012)

Chemistry

Chemical Formula:

Ba(Ti,V³⁺,Cr³⁺)₈O₁₆

Barium Titanium Vanadium Chromium Oxide

Molecular Weight:

803.05 gm

Composition:

Barium

18.81 %

Ba

21.00 %

BaO

Titanium

32.79 %

Ti

54.71 %

TiO₂

Vanadium

15.22 %

V

22.40 %

V₂O₃

Chromium

1.29 %

Cr

1.89 %

Cr₂O₃

Oxygen

31.88 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Oxides

Hey's CIM Ref.:

7.9.29

7 : Oxides and Hydroxides
9 : Oxides of Ti

Related to:

An H2O-free variety of Mannardite. Hollandite Supergroup; Priderite Group.

Members of Group:

Priderite Group: Henrymeyerite, Mannardite, Priderite, Redledgeite 

Varieties:

None

Synonyms:

ICSD 68631, IMA1986-026, PDF 41-1427

Crystal Data

Crystallography:

Tetragonal - Dipyramidal

Crystal Habit:

Crystals, euhedral to subhedral, prismatic, with {100} and {110}, to 1 mm. 

Twinning:

None

Physical Properties

Cleavage:

Interrupted elongation, possibly a parting

Fracture:

Irregular/Uneven

Tenacity:

Brittle

Moh's Hardness:

Vickers: VHN₁₀₀=874 kg/mm²

Density:

4.44 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Optical Properties

Color:

Black; in reflected light, light rose-reddish gray

Transparency:

Opaque

Luster:

Vitreous to adamantine

Bireflectance:

R1–R2: (589) 12.8–20.1

Birefringence:

n/a

Dispersion:

n/a

Pleochroism:

O = pinkish grey, E = light pink, Orientation: E = c

Anisotropism:

Bireflectance: Weak to distinct. Color in reflected light, light rose-reddish gray.

Occurances

Geological Setting:

In a quartz vein.

Common Associations:

Barite, Barytocalcite, Roscoelite, Diopside

Common Impurities:

n/a

Type Locality:

Shiti Mine, Hanbin District, Ankang Prefecture, Shaanxi Province, China

Year Discovered:

1986

View mineral photos:

Ankangite Mineral Photos and Locations

Unusual Gem Categories

Inclusions in Quartz

More Information

Mindat.org
Webmineral.com

Ankangite is a rare Barium Titanium Vanadium Chromium Oxide mineral that can be found as very interesting and attractive radiating acicular "urchin looking" inclusions in Quartz crystals. Quartz crystals with these rare, radiating Ankangite inclusions have been found at Morro Hill near the village of Tomás Gonzaga, Curvelo, Minas Gerais, Brazil. All other locations produce lustrous, black, prismatic Ankangite crystals that have grown on the surfaces of host Quartz not as inclusions within the Quartz.

Ankangite was named for its discovery in the Ankang Prefecture, Shaanxi Province, China (at the Shiti Mine, Hanbin District). Ankangite was approved by the Commission on New Minerals and Mineral Names of the IMA in 1986 but was discredited as a distinct mineral species in 2012 by the IMA as it was determined to be an H2O-free variety of Mannardite.

Locations for Ankangite: at the type locality at the Shiti Mine, Hanbin District, Ankang Prefecture, Shaanxi Province, China. In Brazil as beautiful inclusions in Quartz crystals at Morro Hill near the village of Tomás Gonzaga, Curvelo, Minas Gerais. In Italy at Monte Arsiccio Mine, Sant'Anna di Stazzema, Stazzema, Apuan Alps, Lucca Province, Tuscany. In Russia at the Pereval Marble Quarry, Slyudyanka (Sludyanka), Lake Baikal area, Irkutskaya Oblast', Prebaikalia (Pribaikal'e), Eastern-Siberian Region; and at Vuonnemiok River Valley, Khibiny Massif, Kola Peninsula, Murmanskaja Oblast', Northern Region, Russia.

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