Macdonaldite
A valid IMA mineral species
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About Macdonaldite
Gordon A. Macdonald
Formula:
BaCa4Si16O36(OH)2 · 10H2O
Colour:
White, colourless
Lustre:
Vitreous, Silky
Hardness:
3½ - 4
Specific Gravity:
2.27
Crystal System:
Orthorhombic
Name:
Named in honour of Gordon A. Macdonald (15 October 1911 – 20 June 1978), notable American volcanologist and Senior Professor of Geology at the University of Hawaii at the time of the description. His 1938 Ph.D. thesis "Geology of the Western Sierra Nevada Between Kings and San Joaquin Rivers, California" included this area.
Co-Type Localities:
This page provides mineralogical data about Macdonaldite.
Unique Identifiers
Mindat ID:
2506
Long-form identifier:
mindat:1:1:2506:1
IMA Classification of Macdonaldite
Approved
IMA Formula:
BaCa4Si16O36(OH)2(H2O)6·4H2O
Approval year:
1964
First published:
1965
Classification of Macdonaldite
9.EB.05
9 : SILICATES (Germanates)
E : Phyllosilicates
B : Double nets with 4- and 6-membered rings
9 : SILICATES (Germanates)
E : Phyllosilicates
B : Double nets with 4- and 6-membered rings
72.5.1.3
72 : PHYLLOSILICATES Two-Dimensional Infinite Sheets with Other Than Six-Membered Rings
5 : Two-Dimensional Infinite Sheets with Other Than Six-Membered Rings with corrugated and complex layers
72 : PHYLLOSILICATES Two-Dimensional Infinite Sheets with Other Than Six-Membered Rings
5 : Two-Dimensional Infinite Sheets with Other Than Six-Membered Rings with corrugated and complex layers
14.7.4
14 : Silicates not Containing Aluminum
7 : Silicates of Ba, Sr and Zn
14 : Silicates not Containing Aluminum
7 : Silicates of Ba, Sr and Zn
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 |
|---|---|---|
| Mcd | 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 Macdonaldite
Vitreous, Silky
Transparency:
Transparent, Translucent
Colour:
White, colourless
Streak:
White
Hardness:
3½ - 4 on Mohs scale
Cleavage:
Perfect
Perfect on {010}, good on {001}, poor or a fracture on {100}.
Perfect on {010}, good on {001}, poor or a fracture on {100}.
Density:
2.27(2) g/cm3 (Measured) 2.27 g/cm3 (Calculated)
Optical Data of Macdonaldite
Type:
Biaxial (+/-)
RI values:
nα = 1.518(2) nβ = 1.524(2) nγ = 1.530(2)
2V:
Measured: 90° (5), Calculated: 88°
Max. Birefringence:
δ = 0.012
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:
Low (negative)
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:
weak
Optical Extinction:
X = c; Y = b; Z = a.
Chemistry of Macdonaldite
Mindat Formula:
BaCa4Si16O36(OH)2 · 10H2O
Element Weights:
Common Impurities:
Ti,Al,Fe,Mn,Mg,Sr
Crystallography of Macdonaldite
Crystal System:
Orthorhombic
Cell Parameters:
a = 14.06(1) Å, b = 23.52(2) Å, c = 13.08(1) Å
Ratio:
a:b:c = 0.598 : 1 : 0.556
Unit Cell V:
4,325.44 ų (Calculated from Unit Cell)
Z:
4
Morphology:
Fibrous, in radiating aggregates, and granular. Elongated along [100] and showing forms {010} (major), {001}, and {100).
Comment:
Point Group: 2/m 2/m 2/m or mm2:; Space Group: Bmmb; B2mb; or Bm21 b:
Crystal Structure
Load
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Show
Big Balls | Small Balls | Just Balls | Spacefill
Polyhedra Off | Si Polyhedra | All Polyhedra
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Big Balls | Small Balls | Just Balls | Spacefill
Polyhedra Off | Si Polyhedra | All Polyhedra
Remove metal-metal sticks
Display Options
Black Background | White Background
Perspective On | Perspective Off
2D | Stereo | Red-Blue | Red-Cyan
Black Background | White Background
Perspective On | Perspective Off
2D | Stereo | Red-Blue | Red-Cyan
View
CIF File Best | x | y | z | a | b | c
CIF File Best | x | y | z | a | b | c
Rotation
Stop | Start
Stop | Start
Labels
Console Off | On | Grey | Yellow
Console Off | On | Grey | Yellow
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) |
|---|---|---|---|---|---|---|---|
| 0012053 | Macdonaldite | Cannillo E, Rossi G, Ungaretti L (1968) The crystal structure of macdonaldite Atti della Accademia Nazionale dei Lincei 45 399-414 | 1968 | Fresno County, California, USA | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 6.5 Å | (100) |
| 4.36 Å | (80) |
| 6.3 Å | (50) |
| 3.36 Å | (50) |
| 3.02 Å | (45) |
| 2.74 Å | (45) |
| 8.9 Å | (40) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Near-surface Processes | |
| 22 : Hydration and low-? subsurface aqueous alteration (see also #23) | |
| High-? alteration and/or metamorphism | |
| 32 : Ba/Mn/Pb/Zn deposits, including metamorphic deposits |
Type Occurrence of Macdonaldite
Co-Type Localities:
General Appearance of Type Material:
Vein-forming mineral. Small radiating crystal aggregates up to 12 mm in diameter and individual fibers as much as 6 mm long, but more commonly about 1 mm long.
Place of Conservation of Type Material:
California Division of Mines & Geology, San Francisco, California, USA.
Geological Setting of Type Material:
Sanbornite-quartz-bearing metamorphic rock.
Associated Minerals at Type Locality:
Synonyms of Macdonaldite
Other Language Names for Macdonaldite
Dutch:Macdonaldiet
German:Macdonaldit
Russian:Макдональдит
Simplified Chinese:莫水硅钙钡石
Spanish:Macdonaldita
Traditional Chinese:莫水矽鈣鋇石
Common Associates
Associations Based on Photo Data:
| 6 photos of Macdonaldite associated with Quartz | SiO2 |
| 2 photos of Macdonaldite associated with Pyrrhotite | Fe1-xS |
| 2 photos of Macdonaldite associated with Hydroxyapophyllite-(K) | KCa4(Si8O20)(OH,F) · 8H2O |
| 2 photos of Macdonaldite associated with Opal | SiO2 · nH2O |
| 2 photos of Macdonaldite associated with Titantaramellite | Ba4(Ti,Fe3+,Fe2+,Mg)4(B2Si8O27)O2Clx |
| 2 photos of Macdonaldite associated with Celsian | Ba(Al2Si2O8) |
| 1 photo of Macdonaldite associated with Sanbornite | BaSi2O5 |
| 1 photo of Macdonaldite associated with Kampfite | Ba12(Si11Al5)O31(CO3)8Cl5 |
| 1 photo of Macdonaldite associated with Gillespite | BaFe2+Si4O10 |
| 1 photo of Macdonaldite associated with Diopside | CaMgSi2O6 |
Related Minerals - Strunz-mindat Grouping
| 9.EB. | Natromelansonite | Na3Zr[Si7AlO19] · 4H2O |
| 9.EB.05 | Melansonite | Na◻KZrSi8O19 · 5H2O |
| 9.EB.05 | Rhodesite | KHCa2Si8O19 · 5H2O |
| 9.EB.10 | Hydrodelhayelite | KCa2AlSi7O17(OH)2 · 6H2O |
| 9.EB.10 | Delhayelite | (Na,K)10Ca5Al6Si32O80(Cl2,F2,SO4)3 · 18H2O |
| 9.EB.15 | Monteregianite-(Y) | (Na,K)6(Y,Ca)2Si16O38 · 10H2O |
| 9.EB.20 | Carletonite | KNa4Ca4Si8O18(CO3)4(OH,F) · H2O |
| 9.EB.20 | Fluorcarletonite | KNa4Ca4Si8O18(CO3)4F · H2O |
| 9.EB.25 | Günterblassite | (K,Ca,Ba)2(Fe,Ca,Mg,Na)[(Si,Al)13O25(OH)4] · 7H2O · |
| 9.EB.25 | Hillesheimite | (K,Ca,Ba,◻)2(Mg,Fe,Ca,◻)2[(Si,Al )13O23(OH)6](OH) · 8H2O |
| 9.EB.25 | Umbrianite | K7Na2Ca2[Al3Si10O29]F2Cl2 |
| 9.EB.30 | Fivegite | K4Ca2[AlSi7O17(O2-xOHx)][(H2O)2-xOHx]Cl |
Other Information
Thermal Behaviour:
Gives off water in a closed tube test and fuses at about 5 1/2.
Heated in an electric furnace, it shows no significant change
in appearance until 1200 °C, when it turns opaque white and the weight loss totals 13.7%. At 1300 °C it shows no further
change but may be near its melting point.
Heated in an electric furnace, it shows no significant change
in appearance until 1200 °C, when it turns opaque white and the weight loss totals 13.7%. At 1300 °C it shows no further
change but may be near its melting point.
Notes:
Insoluble in cold acids and bases. Decomposed by boiling 1:1 HCl. After boiling in HCl, a transparent platy silica residue remains.
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 Macdonaldite
mindat.org URL:
https://www.mindat.org/min-2506.html
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Please feel free to link to this page.
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References for Macdonaldite
Localities for Macdonaldite
Showing 11 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 | |
| Sabatini (1899) +8 other references |
USA (TL) | |
| Stinson (1964) +1 other reference |
| Walstrom (n.d.) +3 other references |
| Bob Walstrom | |
| Alfors et al. (1965) +2 other references | |
| Walstrom (n.d.) | |
| Walstrom (n.d.) +2 other references |
| Walstrom (n.d.) | |
| Cooper et al. (1999) |
| Dunning et al. (2003) |
| Walstrom (n.d.) |
Quick NavTopAbout MacdonalditeUnique IdentifiersIMA Classification Classification Mineral SymbolsPhysical Properties Optical Data Chemistry Crystallography Crystal StructureX-Ray Powder DiffractionGeological EnvironmentType Occurrence SynonymsOther LanguagesCommon AssociatesStrunz-MindatOther InformationInternet Links References Localities Locality List
Big Creek, Big Creek-Rush Creek Mining District, Fresno County, California, USA