Alumohydrocalcite
A valid IMA mineral species - grandfathered
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About Alumohydrocalcite
Formula:
CaAl2(CO3)2(OH)4 · 4H2O
Previously assumed to have only three water molecules per formula unit.
Colour:
Chalky white to pale blue, pale yellow, cream, gray; pale rose or brownish pink to dark violet in Cr-bearing varieties
Hardness:
2½
Specific Gravity:
2.21 - 2.24
Crystal System:
Triclinic
Member of:
Name:
In allusion to the composition, containing ALUMinium, water (HYDRated) and a calcium carbonate (CALCITE) component.
Unique Identifiers
Mindat ID:
157
Long-form identifier:
mindat:1:1:157:3
IMA Classification of Alumohydrocalcite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
CaAl2(CO3)2(OH)4·3H2O
First published:
1926
Classification of Alumohydrocalcite
5.DB.05
5 : CARBONATES (NITRATES)
D : Carbonates with additional anions, with H2O
B : With large and medium-sized cations
5 : CARBONATES (NITRATES)
D : Carbonates with additional anions, with H2O
B : With large and medium-sized cations
16b.2.3.1
16b : HYDRATED CARBONATES CONTAINING HYDROXYL OR HALOGEN
2 : AmBn(XO3)pZqxH2O & with (m+n):p = 3:2
16b : HYDRATED CARBONATES CONTAINING HYDROXYL OR HALOGEN
2 : AmBn(XO3)pZq
11.7.7
11 : Carbonates
7 : Carbonates of Al
11 : Carbonates
7 : Carbonates of Al
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 |
|---|---|---|
| Ahcal | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
Pronunciation of Alumohydrocalcite
Pronunciation:
| Play | Recorded by | Country |
|---|---|---|
| Jolyon Ralph | United Kingdom |
Physical Properties of Alumohydrocalcite
Transparency:
Transparent, Translucent, Opaque
Colour:
Chalky white to pale blue, pale yellow, cream, gray; pale rose or brownish pink to dark violet in Cr-bearing varieties
Comment:
colourless in transmitted light
Hardness:
2½ on Mohs scale
Tenacity:
Brittle
Cleavage:
Perfect
On {100}; on {010} imperfect.
On {100}; on {010} imperfect.
Density:
2.21 - 2.24 g/cm3 (Measured) 2.213 g/cm3 (Calculated)
Optical Data of Alumohydrocalcite
Type:
Biaxial (-)
RI values:
nα = 1.485 - 1.502 nβ = 1.553 - 1.562 nγ = 1.570 - 1.585
2V:
Measured: 64° , Calculated: 50° to 60°
Max. Birefringence:
δ = 0.083 - 0.085
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:
None to Very Low
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.
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.
Dispersion:
r > v strong
Optical Extinction:
X = b; Extinction inclined 6°–10°.
Chemistry of Alumohydrocalcite
Mindat Formula:
CaAl2(CO3)2(OH)4 · 4H2O
Previously assumed to have only three water molecules per formula unit.
Previously assumed to have only three water molecules per formula unit.
Element Weights:
Common Impurities:
Cr
Crystallography of Alumohydrocalcite
Crystal System:
Triclinic
Class (H-M):
1 - Pinacoidal
Space Group:
P1
Cell Parameters:
a = 5.71(5) Å, b = 6.54(4) Å, c = 14.6(2) Å
α = 81.8(3)°, β = 83.9(3)°, γ = 86.5(7)°
α = 81.8(3)°, β = 83.9(3)°, γ = 86.5(7)°
Ratio:
a:b:c = 0.873 : 1 : 2.232
Unit Cell V:
537 ų
Morphology:
As fibers and needles, to 2.5 mm; commonly in radial aggregates and spherulites, feltlike crystal linings, and powdery to chalky masses.
Comment:
Space Group: P1 or P1 (chromian).
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 7.21 Å | (30) |
| 6.50 Å | (70) |
| 6.25 Å | (100) |
| 3.23 Å | (60) |
| 2.860 Å | (30) |
| 2.519 Å | (40) |
| 2.039 Å | (50) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 7: Great Oxidation Event | <2.4 |
| 47a : [Near-surface hydration of prior minerals] | |
| 47c : [Carbonates, phosphates, borates, nitrates] |
Geological Setting:
Formed at low temperature by the action of carbonated waters on allophane or dickite in dolomites and limestones; chromian varieties are typically formed near altering chromite from serpentinites.
Type Occurrence of Alumohydrocalcite
General Appearance of Type Material:
Finely porous, chalk-like masses.
Place of Conservation of Type Material:
A.E. Fersman Mineralogical Museum, Academy of Sciences, Moscow, Russia, 77088.
Geological Setting of Type Material:
Limestone and siliceous rock.
Associated Minerals at Type Locality:
Synonyms of Alumohydrocalcite
Other Language Names for Alumohydrocalcite
Varieties of Alumohydrocalcite
| Chromium-bearing Alumohydrocalcite | A chromium-bearing variety of alumohydrocalcite. Cr-dominant samples are grguricite. |
| Knipovichite | Equivalent to Chromian Alumohydrocalcite. Discredited as a distinct species. |
Relationship of Alumohydrocalcite to other Species
Member of:
Other Members of Dresserite Group:
| Dresserite | BaAl2(CO3)2(OH)4 · H2O | Orth. mmm(2/m2/m2/m) |
| Dundasite | PbAl2(CO3)2(OH)4 · H2O | Orth. mmm(2/m2/m2/m) |
| Grguricite | CaCr2(CO3)2(OH)4 · 4H2O | Tric. 1 : P1 |
| Hydrodresserite | BaAl2(CO3)2(OH)4 · 3H2O | Tric. 1 : P1 |
| Kochsándorite | CaAl2(CO3)2(OH)4 · H2O | Orth. mmm(2/m2/m2/m) : Pnma |
| Petterdite | PbCr3+2(CO3)2(OH)4 · H2O | Orth. mmm(2/m2/m2/m) |
| Strontiodresserite | SrAl2(CO3)2(OH)4 · H2O | Orth. mmm(2/m2/m2/m) |
| 'Unnamed (Ca-analogue of Petterdite)' | CaCr3+2(CO3)2(OH)4 · H2O |
Common Associates
Associations Based on Photo Data:
| 11 photos of Alumohydrocalcite associated with Azurite | Cu3(CO3)2(OH)2 |
| 8 photos of Alumohydrocalcite associated with Fluorapatite | Ca5(PO4)3F |
| 8 photos of Alumohydrocalcite associated with Malachite | Cu2(CO3)(OH)2 |
| 6 photos of Alumohydrocalcite associated with Calcite | CaCO3 |
| 5 photos of Alumohydrocalcite associated with Goethite | Fe3+O(OH) |
| 4 photos of Alumohydrocalcite associated with Allophane | (Al2O3)(SiO2)1.3-2 · 2.5-3H2O |
| 3 photos of Alumohydrocalcite associated with Siderite | FeCO3 |
| 3 photos of Alumohydrocalcite associated with Carbonatecyanotrichite | Cu4Al2(CO3,SO4)(OH)12 · 2H2O |
| 2 photos of Alumohydrocalcite associated with Clinopyroxene Subgroup | |
| 2 photos of Alumohydrocalcite associated with Pyrite | FeS2 |
Related Minerals - Strunz-mindat Grouping
| 5.DB. | Rigrahamite | Na2Ca2Th2(CO3)4(HCO3)2(OH)4(H2O)7 |
| 5.DB. | Grguricite | CaCr2(CO3)2(OH)4 · 4H2O |
| 5.DB.05 | Para-alumohydrocalcite | CaAl2(CO3)2(OH)4 · 6H2O |
| 5.DB.05 | Nasledovite | PbMn3Al4(CO3)4(SO4)O5 · 5H2O |
| 5.DB.05 | 'UM1977-02-CO:AlCaH' | Ca6Al2(CO3)3O6 · 32H2O |
| 5.DB.10 | Kochsándorite | CaAl2(CO3)2(OH)4 · H2O |
| 5.DB.10 | Dresserite | BaAl2(CO3)2(OH)4 · H2O |
| 5.DB.10 | Dundasite | PbAl2(CO3)2(OH)4 · H2O |
| 5.DB.10 | 'Unnamed (Ca-analogue of Petterdite)' | CaCr3+2(CO3)2(OH)4 · H2O |
| 5.DB.10 | Petterdite | PbCr3+2(CO3)2(OH)4 · H2O |
| 5.DB.10 | Strontiodresserite | SrAl2(CO3)2(OH)4 · H2O |
| 5.DB.10 | Montroyalite | Sr4Al8(CO3)3(OH,F)26 · 10-11H2O |
| 5.DB.15 | Hydrodresserite | BaAl2(CO3)2(OH)4 · 3H2O |
| 5.DB.20 | Schuilingite-(Nd) | PbCu(Nd,Gd,Sm,Y)(CO3)3(OH) · 1.5H2O |
| 5.DB.25 | Sergeevite | Ca2Mg11(CO3)9(HCO3)4(OH)4 · 6H2O |
| 5.DB.30 | Szymańskiite | [H3O]+8[Hg2]2+8(Ni,Mg)6[CO3]12(OH)12 · 3H2O |
| 5.DB.35 | Lusernaite-(Y) | Y4Al(CO3)2(OH)10F · 6H2O |
| 5.DB.40 | Putnisite | SrCa4Cr3+8(CO3)8SO4(OH)16 · 23H2O |
Other Information
Notes:
Readily soluble in acids. Decomposed by boiling water with separation of calcium carbonate and hydrous aluminum oxide.
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.
Internet Links for Alumohydrocalcite
mindat.org URL:
https://www.mindat.org/min-157.html
Please feel free to link to this page.
Please feel free to link to this page.
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External Links:
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References for Alumohydrocalcite
Reference List:
Localities for Alumohydrocalcite
Showing 60 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.
Argentina | |
| Peña (1970) |
| Raúl Jorge Tauber Larry´s collection |
Austria | |
| Blass et al. (2003) |
| Walter et al. (2021) |
| Niedermayr et al. (1995) |
| Auer (2020) |
Belgium | |
| Fransolet et al. (1975) +2 other references |
| Jockin (en collaboration avec l'université de Liège) +1 other reference | |
| Blondieau et al. (2012) |
France | |
| G. Favreau communication et al. (Allier, France) |
| Queneau (n.d.) +1 other reference |
Germany | |
| Schnorrer-Köhler (1990) |
| Kautz (1968) |
| Blass et al. (1996) |
| Blass et al. (1996) | |
| Blass et al. (1996) |
| Blass et al. (1996) |
| Hentschel (1987) +1 other reference |
| Hentschel (1993) |
Greece | |
| Rieck et al. (2018) |
Hungary | |
| |
| Sajó et al. (2007) |
Italy | |
| Sabelli C. et al. (1996) |
| "Lithothek der Münchener Micromounter" ... |
| www.comune.pisa.it (2000) |
| Neschen (n.d.) |
| Muenchener Micromounter-Lithothek |
| Orlandi et al. (2009) |
| Orlandi (1999) +1 other reference |
| Orlandi et al. (2009) |
| Daleffe et al. (2012) |
Japan | |
| [var: Chromium-bearing Alumohydrocalcite] Hori +1 other reference |
| Mineralogical Society of America - ... |
| Petrov (n.d.) |
| The Mineral Species of Japan (5th ed) |
| Ohe Rikosya specimens (Kyoto) |
Kyrgyzstan | |
| Uvarova et al. (2005) +1 other reference |
Pakistan | |
| Mineralogical Society of America - ... |
Poland | |
| Hoehne K. (1953) |
| Eligiusz Szełęg private collection +2 other references |
| Wojciech Czapliński |
Russia (TL) | |
| Palache et al. (1951) +1 other reference |
Slovakia | |
| Cílek (1999) |
| Bačo |
| Pauliš |
Spain | |
| Bareche (2005) |
| Mineralogistes de Catalunya (1997) |
Turkmenistan | |
| Evseev (1995) | |
UK | |
| Hanson Limited |
| Day (1999) |
| Ryback G. "Alumohydrocalcite from ... |
| Mineralogical Society of America - ... |
| Turner R.W. and Rumsey (2007) +1 other reference |
USA | |
| [var: Chromium-bearing Alumohydrocalcite] Cooper et al. (1975) +2 other references |
| [var: Chromium-bearing Alumohydrocalcite] Dunning (2000) |
| Castor et al. (2004) |
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Laacher See Volcanic Complex, Germany