Demagistrisite
A valid IMA mineral species
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About Demagistrisite
Formula:
BaCa2Mn3+4(Si3O10)(Si2O7)(OH)4 · 3H2O
Colour:
orange brown to red brown
Lustre:
Vitreous
Crystal System:
Orthorhombic
Name:
Named in honor of Leandro De Magistris (1906-1990), former honorary curator of the Genova Mineralogical Museum.
New structure type. Chemically somewhat related to various mineral species, e.g., the unapproved 'bariumbannisterite' or muirite. Described as "the missing link in a polysomatic series from lawsonite to orientite".
Crystal structure (intermediate between that of orientite and noelbensonite) details:
- straight edge-sharing chains of Mn3+-centred octahedra, running along [010],
- they are bridged by disilicate and trisilicate groups;
- cavities within thus formed framework bear two large cation sites.
Crystal structure (intermediate between that of orientite and noelbensonite) details:
- straight edge-sharing chains of Mn3+-centred octahedra, running along [010],
- they are bridged by disilicate and trisilicate groups;
- cavities within thus formed framework bear two large cation sites.
Unique Identifiers
Mindat ID:
53156
Long-form identifier:
mindat:1:1:53156:0
IMA Classification of Demagistrisite
Approved
IMA Formula:
BaCa2Mn3+4(Si3O10)(Si2O7)(OH)4·3H2O
Approval year:
2018
First published:
2021
Type description reference:
Classification of Demagistrisite
9.HA.35
9 : SILICATES (Germanates)
H : Unclassified silicates
A : With Alkali and Alkali-earth Elements
9 : SILICATES (Germanates)
H : Unclassified silicates
A : With Alkali and Alkali-earth Elements
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 |
|---|---|---|
| Dmg | 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 Demagistrisite
Vitreous
Transparency:
Transparent, Translucent
Colour:
Orange brown to red brown
Comment:
orange brown in thin section
Streak:
Beige
Fracture:
Irregular/Uneven
Optical Data of Demagistrisite
Type:
Biaxial (-)
RI values:
nα = 1.805(5) nβ = 1.825(5) nγ = 1.8305(5)
2V:
Measured: 58° (5), Calculated: 54.7°
Max. Birefringence:
δ = 0.026
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.
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:
very strong, r > v
Pleochroism:
Strong
Comments:
X - orange yellow, Y - red brown, Z - red brown; X << Z < Y
Comments:
optical orientation: X = c, Y = b, Z = a
Chemistry of Demagistrisite
Mindat Formula:
BaCa2Mn3+4(Si3O10)(Si2O7)(OH)4 · 3H2O
Element Weights:
Crystallography of Demagistrisite
Crystal System:
Orthorhombic
Class (H-M):
mm2 - Pyramidal
Space Group:
Amm2
Cell Parameters:
a = 16.3160(6) Å, b = 6.1830(2) Å, c = 9.0740(3) Å
Ratio:
a:b:c = 2.639 : 1 : 1.468
Unit Cell V:
915.40 ų (Calculated from Unit Cell)
Morphology:
Needles with square cross-section, typically with irregular terminations, and rarely terminated by a low-angle pyramid.
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 16.21 Å | (49) |
| 4.86 Å | (44) |
| 4.34 Å | (56) |
| 3.196 Å | (43) |
| 2.871 Å | (54) |
| 2.731 Å | (100) |
| 2.671 Å | (74) |
| 2.426 Å | (51) |
Reference:
Comments:
From Type Description.
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| High-? alteration and/or metamorphism | |
| 32 : Ba/Mn/Pb/Zn deposits, including metamorphic deposits |
Type Occurrence of Demagistrisite
General Appearance of Type Material:
(1) tightly intergrown blades, (2) mm-sized prisms & needles with square cross section, often having irregular terminations, rarely terminated by a low-angle pyramid
Place of Conservation of Type Material:
Type material is deposited in the mineralogical collections of the Museum of the Earth Sciences Department, Università di Milano, Via Mangiagalli 34, 20133 Milano, Italy, registration number MCMGPG-H2018-004 (holotype), and the Natural History Museum of Los Angeles County, registration numbers 66942 and 66943 (cotype).
Geological Setting of Type Material:
Mn ore within cherts; the matrix bears braunite, calcite, cryptomelane, orthoclase, and quartz
Associated Minerals at Type Locality:
Synonyms of Demagistrisite
Other Language Names for Demagistrisite
Dutch:Demagistrisiet
German:Demagistrisit
Related Minerals - Strunz-mindat Grouping
| 9.HA. | Shinichengite | Ca5[BSi2O7(OH)2]2 · 6H2O |
| 9.HA. | Kalyuzhnyite-(Ce) | NaKCaSrCeTi(Si8O21)OF(H2O)3 |
| 9.HA. | Moragite | Ca3TiSi2(Al2Si)O14 |
| 9.HA.05 | Ertixiite | Na2Si4O9 |
| 9.HA.10 | Kenyaite | Na2Si22O41(OH)8 · 6H2O |
| 9.HA.20 | Wawayandaite | Ca6Mn2BBe9Si6O23(OH,Cl)15 |
| 9.HA.25 | Magbasite | KBaFe3+Mg7Si8O22(OH)2F6 |
| 9.HA.37 | Donwilhelmsite | CaAl4Si2O11 |
| 9.HA.40 | Kasatkinite | Ba2Ca8B5Si8O32(OH)3 · 6H2O |
| 9.HA.40 | 'Igumnovite' | Ca3Al2[SiO4]2[◻Cl4] |
| 9.HA.42 | Paqueite | Ca3TiSi2(Al,Ti,Si)3O14 |
| 9.HA.42 | Qeltite | Ca3TiSi2(Fe3+2Si)O14 |
| 9.HA.45 | Rippite | K2(Nb,Ti)2(Si4O12)O(O,F) |
| 9.HA.47 | Zagamiite | CaAl2Si3.5O11 |
| 9.HA.50 | Rudenkoite | Sr3(Al3.5Si3.5)O10(OH,O)8Cl2 · H2O |
| 9.HA.50 | 'α-Carnegieite' | NaAlSiO4 |
| 9.HA.52 | 'Atheriastite' | near Ca5MgFeAl6Si8O32 · 5H2O |
| 9.HA.55 | 'Foshallasite' | Ca3[Si2O7] · 3H2O(?) |
| 9.HA.57 | 'Bhreckite' | |
| 9.HA.60 | Nagelschmidtite | Ca7(SiO4)2(PO4)2 |
| 9.HA.65 | Caryochroite | [Na(Sr0.5Ca0.5)Mg]3[Fe3+8Mn(Fe2+0.5◻0.5)]10(Ti2Si12O37)(OH)14(H2O)3 |
| 9.HA.70 | Juanite | Ca10Mg4Al2Si11O39 · 4H2O or near |
| 9.HA.75 | Tacharanite | Ca12Al2Si18O33(OH)36 |
| 9.HA.80 | Oyelite | Ca10Si8B2O29 · 12.5H2O |
| 9.HA.85 | Denisovite | K14+x(Ca,Na,Mn,Fe)48[Si60O162]F16(Ox,OH4-x) · 2H2O |
| 9.HA.90 | Tiettaite | K4Na12Fe3+Si16O41(OH)4 · 2H2O |
Other Information
Notes:
Does not react with HCl at room temperature
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 Demagistrisite
mindat.org URL:
https://www.mindat.org/min-53156.html
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Please feel free to link to this page.
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References for Demagistrisite
Reference List:
Hålenius, U., Hatert, F., Pasero, M., Mills, S. J. (2018) CNMNC Newsletter 45, New minerals and nomenclature modifications approved in 2018. Mineralogical Magazine, 82 (5) 1225-1232 doi:10.1180/mgm.2018.160p.1229
Localities for Demagistrisite
Showing 1 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.
Italy (TL) | |
| Hålenius et al. (2018) +1 other reference |
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Cerchiara Mine, Borghetto di Vara, La Spezia Province, Liguria, Italy