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Mereheadite

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Torr Works Quarry (Merehead Quarry), Cranmore, Somerset, England, UK
© Ian Jones

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Formula:
Pb
 
47
Cl
 
25
(OH)
 
13
O
 
24
(CO
 
3
)(BO
 
3
)
 
2
System:MonoclinicColour:Pale yellow
Hardness:3½
Name:Named after Merehead quarry, Somerset, source of this and other unusual lead secondary minerals.


Related to symesite.

Classification of Mereheadite

IMA status:Approved
Strunz 8th edition ID:3/D.10-80
Nickel-Strunz 10th (pending) edition ID:3.DC.45

3 : HALIDES
D : Oxyhalides, hydroxyhalides and related double halides
C : With Pb (As,Sb,Bi), without Cu
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Type Occurrence of Mereheadite

Type Locality:Torr Works Quarry (Merehead Quarry), Cranmore, Somerset, England, UK

Physical Properties of Mereheadite

Lustre:Vitreous, Resinous
Colour:Pale yellow
Streak:White
Hardness (Mohs):3½

Crystallography of Mereheadite

Crystal System:Monoclinic
Class (H-M):m - Domatic
Cell Parameters:a = 17.372(1) Å, b = 27.9419(19) Å, c = 10.6661(6) Å
β = 93.152(5)°
Ratio:a:b:c = 0.622 : 1 : 0.382
Unit Cell Volume:V 5169.6 ų
Comment:SG Cm; originally reported cell (Welch et al., 1998): C2/c, 5.680, 5.565, 13.143 A, 90.64°.

Optical Data of Mereheadite

Type:Biaxial
RI values: nα = 2.190 nγ = 2.280
Maximum Birefringence:δ = 0.090

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

Chemical Properties of Mereheadite

Formula:
Pb
 
47
Cl
 
25
(OH)
 
13
O
 
24
(CO
 
3
)(BO
 
3
)
 
2
Idealised Formula:
Pb
 
2
Cl(OH)O
Essential elements:B, C, Cl, H, O, Pb
All elements listed in formula:B, C, Cl, H, O, Pb

Relationship of Mereheadite to other Species

Related Minerals - Nickel-Strunz Grouping):

- +
3.DC.05Laurionite
PbCl(OH)
3.DC.05Paralaurionite
PbCl(OH)
3.DC.10Fiedlerite
Pb
 
3
FCl
 
4
(OH) · H
 
2
O
3.DC.15Penfieldite
Pb
 
2
Cl
 
3
(OH)
3.DC.20Laurelite
Pb
 
7
F
 
12
Cl
 
2
3.DC.25Bismoclite
(BiO)Cl
3.DC.25Daubréeite
(BiO)(OH,Cl)
3.DC.25Matlockite
PbFCl
3.DC.25Rorisite
CaFCl
3.DC.25Zavaritskite
(BiO)F
3.DC.25Zhangpeishanite
BaFCl
3.DC.30Nadorite
PbSbClO
 
2
3.DC.30Perite
PbBiClO
 
2
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
Cl
 
2
(OH)(SbO
 
3
,AsO
 
3
)
3.DC.50Blixite
Pb
 
2
(O,OH)
 
2
Cl
3.DC.55Pinalite
Pb
 
3
WO
 
5
Cl
 
2
3.DC.60Symesite
Pb
 
10
Cl
 
4
O
 
7
(SO
 
4
) · H
 
2
O
3.DC.65Ecdemite
Pb
 
6
Cl
 
4
(As
 
2
O
 
7
)
3.DC.65Heliophyllite
Pb
 
6
Cl
 
4
(As
 
2
O
 
7
)
3.DC.70Mendipite
Pb
 
3
Cl
 
2
O
 
2
3.DC.75Damaraite
Pb
 
3
Cl(OH)O
 
2
3.DC.80Onoratoite
Sb
 
8
Cl
 
2
O
 
11
3.DC.85Cotunnite
PbCl
 
2
3.DC.90Pseudocotunnite
K
 
2
PbCl
 
4
3.DC.95Barstowite
Pb
 
4
Cl
 
6
(CO
 
3
) · H
 
2
O

Other Names for Mereheadite

Synonyms:
IMA1996-045
Other Languages:
German:Mereheadit
Spanish:Mereheadita

Other Information

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 Mereheadite

Reference List:

- +
Welch, M. D., Criddle, A. J. and Symes, R. F. (1998): Mereheadite, Pb2O(OH)Cl: a new litharge-related oxychloride from Merehead Quarry, Cranmore, Somerset. Mineralogical Magazine: 62: 387-393.

Krivovichev, S.V., Turner, R., Rumsey, M., Siidra, O.I., Kirk. C.A. (2009): The crystal structure and chemistry of mereheadite. Mineralogical Magazine, 73, 103-117.

Internet Links for Mereheadite

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  • Raman and XRD data at RRUFF project
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  • Mereheadite details from Handbook of Mineralogy (PDF)
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    • Localities for Mereheadite

    The map shows a selection of localities that have latitude and longitude coordinates recorded. Click on the symbol to view information about a locality. The symbol next to localities in the list can be used to jump to that position on the map.
    Hide Locality List
    (TL) indicates type locality. ? indicates mineral may be doubtful at this locality. All other localities listed without reference should be considered as uncertain and unproven until references can be found.
    Germany
     
    • Baden-Württemberg
      • Black Forest
        • Wolfach
          • Oberwolfach
            • Rankach valley
    		KOLITSCH, U. (2000): Eine durch Betoneinwirkung entstandene Paragenese von Blei-Verbindungen aus der Grube Clara im mittleren Schwarzwald. - Erzgräber 14, 48-53; WALENTA, K. (1999): Neue Mineralfunde von der Grube Clara. 8. Folge, 2. Teil. Lapis 24 (12), 40-44
    UK
     
    • England
      • Somerset
        • Cranmore
    		[Min.Mag.(1998) 62, 387-393; J. Russel Soc 2:2 p29]; Turner, R.W., (2005) A New Find of Lead Oxychlorides at Torr Works, Somerset. Russell Society Newsletter, No. 47, September 2005; Turner, R.W., (2006) A Mechanism for the formation of the Mineralised Mn Deposits at Merehead Quarry, Cranmore, Somerset, England. Min. Mag. vol. 70, no. 6, pp 629 - 653; Krivovichev, S.V., Turner, R.W., Rumsey, M.S., Siidra, O.I. and Kirk, C.A. (2009). The crystal structure and chemistry of mereheadite. Mineralogical Magazine, 73, 75-89; Turner, R.W. and Rumsey, M.S. (2010): Mineral Relationships in the Mendip Hills. Journal of the Russell Society, vol 13, pp 3-46;
        • Westbury on Trym
    		BMS Database
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