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Bismoclite

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Croft Gothal Mine, St Hilary, Mount's Bay District, Cornwall, England, UK
© Steve Rust

Show Bismoclite Photos (5)
Formula:
BiOCl
System:TetragonalColour:Cream-white, greyish, ...
Hardness:2 - 2½
Name:In allusion to its composition: a BISMuth OxyChLoride.


Matlockite Group.

Very plastic.

Classification of Bismoclite

IMA status:Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
Strunz 8th edition ID:3/D.0-40
Nickel-Strunz 10th (pending) edition ID:3.DC.25

3 : HALIDES
D : Oxyhalides, hydroxyhalides and related double halides
C : With Pb (As,Sb,Bi), without Cu
Dana 8th edition ID:10.2.1.2

10 : OXYHALIDES AND HYDROXYHALIDES
2 : A(O,OH)Xq
Hey's CIM Ref.:8.9.5

8 : Halides - Fluorides, Chlorides, Bromides and Iodides; also Fluoborates and Fluosilicates
9 : Halides of Sb and Bi
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Type Occurrence of Bismoclite

Type Locality:Jakkalswater (Jackal's Water; Noumas I pegmatite; Blesberg mine), Steinkopf, Namaqualand, Northern Cape Province, South Africa
Year of Discovery:1935
Geological Setting of type material:In an alluvial specimen, found near bismuth-bearing granite pegmatites
Associated Minerals at type locality:
Mica GroupBismutite

Occurrences of Bismoclite

Geological Setting:In granite pegmatites; in greisen

Physical Properties of Bismoclite

Lustre:Greasy, Silky, Pearly, Dull, Earthy
Diaphaneity (Transparency):Transparent, Translucent
Colour:Cream-white, greyish, yellowish brown; colourless in thin section
Hardness (Mohs):2 - 2½
Tenacity:Elastic
Cleavage:Perfect
On {001}
Density (measured):7.36 g/cm3
Density (calculated):7.784 g/cm3

Crystallography of Bismoclite

Crystal System:Tetragonal
Class (H-M):4/mmm (4/m 2/m 2/m) - Ditetragonal Dipyramidal
Space Group:P4/nmm {P4/n 21/m 2/m}
Cell Parameters:a = 3.887Å, c = 7.354Å
Ratio:a:c = 1 : 1.892
Unit Cell Volume:V 111.11 ų (Calculated from Unit Cell)
Z:2
Morphology:Crystals minute, scaly or thin rectangular, rarely with corners truncated at 45°; often columnar-fibrous, earthy, compact or massive.
X-Ray Powder Diffraction:
d-spacingIntensity
3.44 (100)
2.677 (95)
2.753 (75)
7.38 (40)
1.946 (35)
2.205 (30)
Comments:Recorded on synthetic material

Optical Data of Bismoclite

Type:Uniaxial (-)
RI values: nω = 2.150 nε = 1.910
Maximum Birefringence:δ = 0.240

Chart shows birefringence interference colour range (at 30µm thickness) and does not take into account mineral colouration.
Surface Relief:Very High

Chemical Properties of Bismoclite

Formula:
BiOCl
Essential elements:Bi, Cl, O
All elements listed in formula:Bi, Cl, O
Analytical Data:Chemical analyses of material from Jakkalswater, South Africa (1) and from Goldfield, Nevada, USA (2), the latter recalculated to 100.00 wt.-% after deduction of quartz (34.81 wt.-%) and Fe2O3 (0.28 wt.-%)
            (1)      (2)

Fe2O3      (0.12)
Bi2O3     (88.49)  (88.53)
Cl        (13.00)  (12.51)
H2O+       (0.87)   (1.58)
H2O-                (0.20)
insol.     (0.77)
-O = Cl2   (2.93)   (2.82)

sum       100.32   100.00 wt.-%
Common Impurities:Fe,OH

Relationship of Bismoclite to other Species

Member of Group:
Matlockite Group:
MXY
Related Minerals - Nickel-Strunz Grouping):

- +
3.DC.05Laurionite
PbClOH
3.DC.05Paralaurionite
PbClOH
3.DC.10Fiedlerite
Pb
 
3
Cl
 
4
F(OH)·H
 
2
O
3.DC.15Penfieldite
Pb
 
2
[OH|Cl
 
3
]
3.DC.20Laurelite
Pb(F,Cl,OH)
 
2
3.DC.25Daubréeite
BiO(OH,Cl)
3.DC.25Matlockite
PbFCl
3.DC.25Rorisite
CaFCl
3.DC.25Zavaritskite
BiOF
3.DC.25Zhangpeishanite
BaFCl
3.DC.30Nadorite
PbSb[O
 
2
|Cl]
3.DC.30Perite
PbBi[O
 
2
|Cl]
3.DC.35Aravaipaite
Pb
 
3
[F
 
3
|AlF
 
6
] · H
 
2
O
3.DC.37Calcioaravaipaite
PbCa
 
2
[(F,OH)
 
3
|AlF
 
6
] · H
 
2
O
3.DC.40Thorikosite
Pb
 
3
[OH|(SbO
 
3
,AsO
 
3
)|Cl
 
2
]
3.DC.45Mereheadite
Pb
 
47
O
 
24
(OH)
 
13
Cl
 
25
(BO
 
3
)
 
2
(CO3)
3.DC.50Blixite
Pb
 
2
[(O,OH)
 
2
|Cl]
3.DC.55Pinalite
Pb
 
3
WO
 
5
Cl
 
2
3.DC.60Symesite
Pb
 
10
[O
 
7
|SO
 
4
|Cl
 
4
] · H
 
2
O
3.DC.65Ecdemite
Pb
 
6
[As
 
2
O
 
7
|Cl
 
4
]
3.DC.65Heliophyllite
Pb
 
3
AsO
 
4-n
Cl
 
2n+1
3.DC.70Mendipite
Pb
 
3
[O
 
2
|Cl
 
2
]
3.DC.75Damaraite
Pb
 
3
[O
 
2
|OH|Cl]
3.DC.80Onoratoite
Sb
 
8
O
 
11
Cl
 
2
3.DC.85Cotunnite
PbCl
 
2
3.DC.90Pseudocotunnite
K
 
2
PbCl
 
4
3.DC.95Barstowite
Pb
 
4
[Cl
 
6
|CO
 
3
] · H
 
2
O
Related Minerals - Hey's Index Grouping:

- +
8.9.1Onoratoite
Sb
 
8
O
 
11
Cl
 
2
8.9.2Kelyanite
(Hg
2+
 
)
 
6
(SbO
 
6
)BrCl
 
2
8.9.3Gananite
BiF
 
3
8.9.4Zavaritskite
BiOF
8.9.6Daubréeite
BiO(OH,Cl)
8.9.7Perite
PbBi[O
 
2
|Cl]

Other Names for Bismoclite

Other Languages:
German:Bismoclit
Russian:Бисмоклит
Spanish:Bismoclita

Other Information

Other Information:Totally soluble in acids. Re-precipitates upon considerable dilution.

Very plastic.
Health Warning:No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

References for Bismoclite

Reference List:Means (1916) American Journal of Science: 41: 125 (as Daubréeite ?).

Larsen, E.S. (1921) The Microscopic Determination of the Nonopaque Minerals, First edition, USGS Bulletin 679: 66.

Bannister (1935) Mineralogical Magazine: 24: 49.

Mountain (1935) Mineralogical Magazine: 24: 59.

American Mineralogist (1935), 20, 813.

Mountain, E. D. (1937): Two new bismuth minerals from South Africa. Mineralogical Magazine 24, 59-64.

Frondel, C. (1943) American Mineralogist: 28: 526.

Palache, Charles, Harry Berman & Clifford Frondel (1951), The System of Mineralogy of James Dwight Dana and Edward Salisbury Dana Yale University 1837-1892, Volume II: Halides, Nitrates, Borates, Carbonates, Sulfates, Phosphates, Arsenates, Tungstates, Molybdates, Etc. John Wiley and Sons, Inc., New York, 7th edition, revised and enlarged: 60-62.

Keramidas, K. G., Voutsas, G. P. and Rentzepris, P. I. (1993): The crystal structure of BiOCl. Zeitschrift für Kristallographie 205, 35-40.

Anthony, J. W. et al. (1997): Handbook of Mineralogy, Vol. 3, 61.

Internet Links for Bismoclite

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    Localities for Bismoclite

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