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Eglestonite

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Landsberg Mt. (Moschellandsberg Mt.), Obermoschel, Rhineland-Palatinate, Germany
© Thomas Witzke

Show Eglestonite Photos (7)
Formula:
[Hg
1+
2
]
 
3
[O|OH|Cl
 
3
]
System:IsometricColour:Yellow, orange-yellow, ...
Lustre:Adamantine, ResinousHardness:2½
Name:After Thomas E. Egleston (1832-1900) Professor of Mineralogy and Metallurgy, Columbia University, New York.


Eglestonite-Kadyrelite Series

Eglestonite is an alteration product of other mercury minerals (native Mercury, Cinnabar, etc.)

Not to be confused with the silicate eggletonite.

Classification of Eglestonite

IMA status:Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
Strunz 8th edition ID:3/D.06-40
Nickel-Strunz 10th (pending) edition ID:3.DD.05

3 : HALIDES
D : Oxyhalides, hydroxyhalides and related double halides
D : With Hg
Dana 8th edition ID:10.5.4.1

10 : OXYHALIDES AND HYDROXYHALIDES
5 : Am(O,OH)pXq
Hey's CIM Ref.:8.5.6

8 : Halides - Fluorides, Chlorides, Bromides and Iodides; also Fluoborates and Fluosilicates
5 : Halides of Zn and Hg
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Type Occurrence of Eglestonite

Type Locality:Terlingua District, Brewster Co., Texas, USA
Year of Discovery:1903
Associated Minerals at type locality:
TerlinguaiteMontroyditeMercuryCalomelCalcite

Physical Properties of Eglestonite

Lustre:Adamantine, Resinous
Diaphaneity (Transparency):Translucent
Colour:Yellow, orange-yellow, brown; turns dark brownish, then black, on exposure to light; yellow-brown to brown (transmitted light)
Streak:Yellow to greenish-yellow
Hardness (Mohs):2½
Tenacity:Brittle
Fracture:Irregular/Uneven, Conchoidal
Density (measured):8.33 - 8.45 g/cm3
Density (calculated):8.61 g/cm3

Crystallography of Eglestonite

Crystal System:Isometric
Class (H-M):m3m (4/m 3 2/m) - Hexoctahedral
Space Group:Ia3d {I41/a 3 2/d}
Cell Parameters:a = 16.03Å
Unit Cell Volume:V 4,119.08 ų (Calculated from Unit Cell)
Morphology:Dodecahedral, with striations parallel to the edges, and elongated on [001] at times, into almost hair-like forms. Octahedral and cubic forms less common. Massive; as crusts.

Optical Data of Eglestonite

Type:Isotropic
Comments:Exhibits weak anomalous birefringence at times.

Blackened immediately by hydrogen sulfide or ammonia. Decomposed by acids with separation of Calomel.

Chemical Properties of Eglestonite

Formula:
[Hg
1+
2
]
 
3
[O|OH|Cl
 
3
]
Essential elements:Cl, H, Hg, O
All elements listed in formula:Cl, H, Hg, O

Relationship of Eglestonite to other Species

Series:Forms a series with Kadyrelite (see here)
Common Associates:
MercuryCinnabarCalomel
Related Minerals - Nickel-Strunz Grouping):

- +
3.DD.05Kadyrelite
Hg
 
4
(Br,Cl)
 
2
O
3.DD.10Poyarkovite
Hg
 
3
ClO
3.DD.15Hanawaltite
Hg
 
6
Hg[Cl,(OH)]
 
2
O
 
3
3.DD.20Terlinguaite
Hg
 
2
ClO
3.DD.25Pinchite
Hg
 
5
O
 
4
Cl
 
2
3.DD.30Gianellaite
[Hg
 
2
N]
+
2
SO
 
4
3.DD.30Mosesite
[Hg
 
2
N]
+
 
(Cl,SO
 
4
,MoO
 
4
) · H
 
2
O
3.DD.35Kleinite
[Hg
 
2
N]
+
3
Cl
 
2
S
 
0.5
 · H
 
2
O
3.DD.40Tedhadleyite
Hg
2+
 
Hg
1+
10
O
 
4
I
 
2
(Cl,Br)
 
2
3.DD.45Vasilyevite
[Hg
1+
2
]
 
10
[O
 
6
|I
 
3
|Br
 
2
|Cl|CO
 
3
]
3.DD.50Aurivilliusite
(Hg-Hg)
2+
 
Hg
2+
2
[O|(I,Br,Cl)]
 
2
3.DD.55Terlinguacreekite
Hg
2+
3
O
 
2
Cl
 
2
3.DD.60Kelyanite
(Hg
2+
 
)
 
6
(SbO
 
6
)BrCl
 
2
3.DD.65Comancheite
Hg
 
13
(Cl,Br)
 
8
O
 
9
Related Minerals - Hey's Index Grouping:

- +
8.5.1Simonkolleite
Zn
 
5
[(OH)
 
8
|Cl
 
2
] · H
 
2
O
8.5.2Calomel
Hg
 
2
Cl
 
2
8.5.3Terlinguaite
Hg
 
2
ClO
8.5.4Poyarkovite
Hg
 
3
ClO
8.5.5Pinchite
Hg
 
5
O
 
4
Cl
 
2
8.5.7Kadyrelite
Hg
 
4
(Br,Cl)
 
2
O
8.5.8Comancheite
Hg
 
13
(Cl,Br)
 
8
O
 
9
8.5.9Kuzminite
Hg
 
2
(Br,Cl)
 
2
8.5.10Moschelite
Hg
 
2
I
 
2
8.5.11Tocornalite
(Ag,Hg)I

Other Names for Eglestonite

Other Languages:
German:Eglestonit
Russian:Эглестонит
Spanish:Eglestonita

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 Eglestonite

Reference List:Moses (1903) American Journal of Science: 16: 253.

Hillebrand and Schaller (1909) USGS Bulletin 405: 143.

Rogers (1911) American Journal of Science: 32: 48.

Bird (1932) American Mineralogist: 17: 541.

Hedlik (1948) Experientia, Basel: 4: 66.

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: 51-52.

American Mineralogist (1977): 62: 396.

Mereiter, K., J. Zeeman, and A.W. Hewat (1992) Eglestonite, [Hg2]3Cl3O2H: confirmation of the chemical formula by neutron powder diffraction. American Mineralogist: 77: 839–842.

Internet Links for Eglestonite

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  • Raman and XRD data at RRUFF project
  • American Mineralogist Crystal Structure Database
  • Search for Eglestonite in the Natural History Museum (London) online catalogue
  • Eglestonite details from Handbook of Mineralogy (PDF)
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    Localities for Eglestonite

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