Montroydite
A valid IMA mineral species - grandfathered
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About Montroydite
Formula:
HgO
Colour:
Deep red, brownish red to brown; Orange-red to pale yellow in transmitted light, with decreasing thickness
Lustre:
Sub-Adamantine, Vitreous
Hardness:
1½ - 2
Specific Gravity:
11.23
Crystal System:
Orthorhombic
Name:
After Montroyd Sharpe (b. 1861 England), an owner of the Terlingua, Texas, USA, mine where it was found. (He resided in Santa Cruz California in the 1930's and donated his mineral collection to museum in city).
Type Locality:
This page provides mineralogical data about Montroydite.
Unique Identifiers
Mindat ID:
2771
Long-form identifier:
mindat:1:1:2771:3
IMA Classification of Montroydite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
Hg2+O
Classification of Montroydite
4.AC.15
4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
A : Metal: Oxygen = 2:1 and 1:1
C : M:O = 1:1 (and up to 1:1.25); with large cations (+- smaller ones)
4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
A : Metal: Oxygen = 2:1 and 1:1
C : M:O = 1:1 (and up to 1:1.25); with large cations (+- smaller ones)
4.2.6.1
4 : SIMPLE OXIDES
2 : AX
4 : SIMPLE OXIDES
2 : AX
7.5.12
7 : Oxides and Hydroxides
5 : Oxides of Zn, Cd and Hg
7 : Oxides and Hydroxides
5 : Oxides of Zn, Cd and Hg
Mineral Symbols
As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
| Symbol | Source | Reference for Standard |
|---|---|---|
| Mtyd | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
Physical Properties of Montroydite
Sub-Adamantine, Vitreous
Transparency:
Transparent, Translucent
Colour:
Deep red, brownish red to brown; Orange-red to pale yellow in transmitted light, with decreasing thickness
Streak:
Yellow-brown
Hardness:
1½ - 2 on Mohs scale
Tenacity:
Sectile
Cleavage:
Perfect
Perfect {010}.
Perfect {010}.
Density:
11.23 g/cm3 (Measured) 11.22 g/cm3 (Calculated)
Optical Data of Montroydite
Type:
Biaxial (+)
RI values:
nα = 2.37 nβ = 2.5 nγ = 2.65
Max. Birefringence:
δ = 0.280
Based on recorded range of RI values above.
Based on recorded range of RI values above.
Interference Colours:
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
The colours simulate birefringence patterns seen in thin section under crossed polars. They do not take into account mineral colouration or opacity.
Michel-Levy Bar The default colours simulate the birefringence range for a 30 µm thin-section thickness. Adjust the slider to simulate a different thickness.
Grain Simulation You can rotate the grain simulation to show how this range might look as you rotated a sample under crossed polars. Each grain retains its interference colour (retardation) while its brightness falls to black at extinction and reaches a maximum between extinction positions.
Surface Relief:
Very High (positive)
Relative to Canada balsam mounting medium (n ≈ 1.537).
Relative to Canada balsam mounting medium (n ≈ 1.537).
This shows the grain boundary and Becke line effect under plane-polarised
light, based on the contrast between this mineral's average refractive
index and the mounting medium. It does not take into account mineral
colouration.
In focus
Interference Figure:
This shows the idealized biaxial acute bisectrix (Bxa) interference figure
- the conoscopic view for a grain cut perpendicular to the acute bisectrix, using
this mineral's 2V. The two small white dots mark the melatopes - the points
where the two optic axes emerge - and are shown only when they fall within the
field of view. The coloured bands are isochromatics, and the dark bands are
isogyres.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
No measured or calculated 2V is on file for this mineral, so the value used here (91°) is estimated from its recorded refractive indices and optic sign, not from a direct 2V measurement.
Rotate the stage: at 0°/90° the isogyres form a cross through the melatopes; at 45° they pull apart into curved hyperbolas. That splitting on rotation - absent in a uniaxial figure - is the standard diagnostic test for telling biaxial minerals from uniaxial ones. If 2V is large, the melatopes may fall outside the field of view, as they often do at the microscope too.
No measured or calculated 2V is on file for this mineral, so the value used here (91°) is estimated from its recorded refractive indices and optic sign, not from a direct 2V measurement.
Dispersion:
relatively strong
Chemistry of Montroydite
Mindat Formula:
HgO
Elements listed:
Crystallography of Montroydite
Crystal System:
Orthorhombic
Class (H-M):
mmm(2/m2/m2/m) - Dipyramidal
Space Group:
Pmmn
Cell Parameters:
a = 5.52 Å, b = 6.6 Å, c = 3.52 Å
Ratio:
a:b:c = 0.836 : 1 : 0.533
Unit Cell V:
128.24 ų (Calculated from Unit Cell)
Morphology:
Long prismatic [001]; also equant or rarely flattened {111}. Terminal faces often striated; on {011} parallel [100], on {201} parallel [101], the pyramids often with several sets of striae. As worm-like, tubular, or spherical aggregates consisting usually of minute prismatic crystals. Massive, powdery, or banded. Crystals often bent or twisted.
Twinning:
Crystals glide readily: bent-gliding and twist-gliding with T{010} and t[001]; also other, unidentified gliding elements.
Crystallographic forms of Montroydite
Crystal Atlas:
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Montroydite no.1 - Goldschmidt (1913-1926)
Montroydite no.14 - {011} - Goldschmidt (1913-1926)
3d models and HTML5 code kindly provided by
www.smorf.nl.
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Crystal Structure
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Data courtesy of the American Mineralogist Crystal Structure Database. Click on an AMCSD ID to view structure
| ID | Species | Reference | Link | Year | Locality | Pressure (GPa) | Temp (K) |
|---|---|---|---|---|---|---|---|
| 0011897 | Montroydite | Aurivillius K (1964) Least-squares refinement of the crystal structures of orthorhombic HgO and of Hg2O2NaI Acta Chemica Scandinavica 18 1305-1306 | 1964 | synthetic | 0 | 293 |
CIF Raw Data - click here to close
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 7: Great Oxidation Event | <2.4 |
| 47h : [Near-surface oxidized, dehydrated minerals] |
Type Occurrence of Montroydite
Other Language Names for Montroydite
Common Associates
Associations Based on Photo Data:
| 32 photos of Montroydite associated with Native Mercury | Hg |
| 29 photos of Montroydite associated with Quartz | SiO2 |
| 24 photos of Montroydite associated with Cinnabar | HgS |
| 21 photos of Montroydite associated with Edgarbaileyite | [Hg2]2+3[Si2O7] |
| 7 photos of Montroydite associated with Terlinguaite | [Hg3]4+Hg2+Cl2O2 |
| 6 photos of Montroydite associated with Wattersite | [Hg2]2+2Hg2+[CrO4]O2 |
| 6 photos of Montroydite associated with Eglestonite | [Hg2]2+3OCl3(OH) |
| 5 photos of Montroydite associated with Calcite | CaCO3 |
| 4 photos of Montroydite associated with Kleinite | (Hg2N)(Cl,SO4) · nH2O |
| 3 photos of Montroydite associated with Dolomite | CaMg(CO3)2 |
Related Minerals - Strunz-mindat Grouping
| 4.AC.05 | Swedenborgite | NaBe4Sb5+O7 |
| 4.AC.10 | Brownmillerite | Ca2Fe3+AlO5 |
| 4.AC.10 | Shulamitite | Ca3TiFe3+AlO8 |
| 4.AC.10 | Sharyginite | Ca3TiFe2O8 |
| 4.AC.10 | Srebrodolskite | Ca2Fe3+2O5 |
| 4.AC.20 | Romarchite | SnO |
| 4.AC.20 | Litharge | PbO |
| 4.AC.25 | Massicot | PbO |
| 4.AC.30 | Nataliakulikite | Ca4Ti2(Fe3+,Fe2+)(Si,Fe3+,Al)O11 |
Other Information
Health Risks:
Contains mercury - always wash hands after handling. Avoid inhaling dust when handling or breaking. Never lick or ingest.
Internet Links for Montroydite
mindat.org URL:
https://www.mindat.org/min-2771.html
Please feel free to link to this page.
Please feel free to link to this page.
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References for Montroydite
Reference List:
Moses, A. J. (1904) Eglestonit, Terlinguaït und Montroydit, neue Quecksilbermineralien von Terlingua in Texas. Zeitschrift für Kristallographie, 39 (1). 3-13 doi:10.1524/zkri.1904.39.1.3
Hillebrand, W.F.; Schaller, W.T. (1909) The mercury minerals from Terlingua, Texas. Bulletin 405. US Geological Survey p.1-174. doi:10.3133/b405 p.47
Bird, Paul H. (1932) A new occurrence and x-ray study of mosesite. American Mineralogist, 17 (12) 541-550
Woodhouse, C. D. (1934) A new occurrence of montroydite in California. American Mineralogist, 19 (12) 603-604
Aurivillius, K. (1956) The crystal structure of mercury (II)-oxide. Acta Crystallographica, 9 (8) 685-686 doi:10.1107/s0365110x56001881
Aurivillius, Karin, Rossotti, Hazel, Taugbøl, K., Theorell, Hugo, Thorell, B. (1956) The Crystal Structure of Mercury(II)oxide Studied by X-Ray and Neutron Diffraction Methods. Acta Chemica Scandinavica, 10. 852-866 doi:10.3891/acta.chem.scand.10-0852
Localities for Montroydite
Showing 37 localities.
symbol to view information about a locality.
The Locality List
- This locality has map coordinates listed.
- This locality has estimated coordinates.
ⓘ - Click for references and further information on this occurrence.
? - Indicates mineral may be doubtful at this locality.
- Good crystals or important locality for species.
- World class for species or very significant.
(TL) - Type Locality for a valid mineral species.
(FRL) - First Recorded Locality for everything else (eg varieties).
All localities listed without proper references should be considered as questionable.
Australia | |
| Bottrill et al. (2020) |
Belgium | |
| perso.infonie.be (2004) |
China | |
| Deqian Wang and Yiting Hou (1987) |
| Xiaoming Qu et al. (2001) |
Italy | |
| Manfred Kampf collection +2 other references |
| |
Kyrgyzstan | |
| Vasil'yev et al. (1982) +2 other references |
| Kolesar et al. (1993) | |
Mexico | |
| Gallagher et al. (1948) |
| Panczner (1987) | |
| Panczner (1987) |
Russia | |
| Silyanov et al. (2021) |
| Canadian Mineralogist Feb. 1999 +1 other reference |
| Pervukhina et al. (2003) |
Spain | |
| Sainz de Baranda Graf et al. (2019) |
| Calvo Rebollar et al. (2022) +1 other reference |
USA | |
| Roberts et al. (2003) |
| Pemberton (1983) +1 other reference |
| Bradley (1938) +3 other references |
| Pemberton (1983) +1 other reference |
| Kim et al. (2004) |
| Canadian Mineralogist: 34: 61-72. +1 other reference |
| Murdoch et al. (1966) |
| Woodhouse (1934) +2 other references |
| Mining and Scientific Press (1868) +2 other references | |
| Woodhouse (1934) +1 other reference | |
| Bradley (1938) +3 other references |
| Bailey (1946) +3 other references |
| Castor et al. (2004) |
| Castor et al. (2004) |
| Castor et al. (2004) |
| Castor et al. (2004) |
| Castor et al. (2004) |
| John et al. (1989) | |
| Castor et al. (2004) |
| Smith (1991) |
| American Journal of Science (1903) +2 other references |
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Socrates Mine, Castle Rock Springs area, West Mayacmas Mining District, Sonoma County, California, USA