Scawtite
A valid IMA mineral species - grandfathered
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About Scawtite
Formula:
Ca7(Si3O9)2CO3 · 2H2O
Colour:
Colourless
Lustre:
Vitreous
Hardness:
4½ - 5
Specific Gravity:
2.71
Crystal System:
Monoclinic
Name:
Named by Cecil Edgar Tilley (Professor of Petrology and Geology at Cambridge University) in 1930 after its discovery locality, Scawt Hill, Larne, Co. Antrim, Northern Ireland, UK.
Type Locality:
This page provides mineralogical data about Scawtite.
Unique Identifiers
Mindat ID:
3552
Long-form identifier:
mindat:1:1:3552:7
IMA Classification of Scawtite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
Ca7(Si3O9)2(CO3)·2H2O
First published:
1930
Classification of Scawtite
9.CK.15
9 : SILICATES (Germanates)
C : Cyclosilicates
K : [Si6O18]12- 6-membered single rings, with insular complex anions
9 : SILICATES (Germanates)
C : Cyclosilicates
K : [Si6O18]12- 6-membered single rings, with insular complex anions
64.2.1.1
64 : CYCLOSILICATES Rings with Other Anions and Insular Silicate Groups
2 : Rings with Other Anions and Insular Silicate Groups: 3-membered rings with other anion groups
64 : CYCLOSILICATES Rings with Other Anions and Insular Silicate Groups
2 : Rings with Other Anions and Insular Silicate Groups: 3-membered rings with other anion groups
17.4.4
17 : Silicates Containing other Anions
4 : Silicates with carbonates
17 : Silicates Containing other Anions
4 : Silicates with carbonates
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 |
|---|---|---|
| Scw | 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 Scawtite
Vitreous
Transparency:
Transparent
Colour:
Colourless
Hardness:
4½ - 5 on Mohs scale
Cleavage:
Imperfect/Fair
{010} fair
{100} poor
{010} fair
{100} poor
Density:
2.71 g/cm3 (Measured) 2.74 g/cm3 (Calculated)
Optical Data of Scawtite
Type:
Biaxial (+)
RI values:
nα = 1.597 - 1.603 nβ = 1.606 - 1.609 nγ = 1.618 - 1.621
2V:
Measured: 74° to 78°, Calculated: 74°
Max. Birefringence:
δ = 0.018 - 0.021
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:
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:
r < v weak
Chemistry of Scawtite
Mindat Formula:
Ca7(Si3O9)2CO3 · 2H2O
Element Weights:
Common Impurities:
Ti,Al,Fe,Mn,Mg
Chemical Analysis
Oxide wt%:
| 1 | |
|---|---|
| CaO | 46.4 % |
| SiO2 | 34.2 % |
| CO2 | 18.0 % |
| Total: | 98.6 % |
Crystallography of Scawtite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
B2/m
Setting:
I2/m
Cell Parameters:
a = 10.118(3) Å, b = 15.187(4) Å, c = 6.626(1) Å
β = 100.55(2)°
β = 100.55(2)°
Ratio:
a:b:c = 0.666 : 1 : 0.436
Unit Cell V:
1,000.95 ų (Calculated from Unit Cell)
Z:
2
Morphology:
parallel to slightly divergent aggregates
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) |
|---|---|---|---|---|---|---|---|
| 0006058 | Scawtite | Grice J D (2005) The structure of spurrite, tilleyite and scawtite, and relationships to other silicate-carbonate minerals The Canadian Mineralogist 43 1489-1500 |  | 2005 | Scawt Hill, near Larne, County Antrim, Ireland | 0 | 293 |
| 0020470 | Scawtite | Zhang L, Fu P, Yang H, Yu K, Zhou Z (1992) Crystal structure of Scawtite Chinese Science Bulletin 37 930-934 | 1992 | Zoulou iron deposit, Anhui Province, China | 0 | 293 | |
| 0000391 | Scawtite | Pluth J J, Smith J V (1973) The crystal structure of scawtite Note sample is from Crestmore, California, USA American Mineralogist 58 1097-1097 | 1973 | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 3.04 Å | (10) |
| 1.898 Å | (6) |
| 2.495 Å | (5) |
| 2.24 Å | (5) |
| 4.56 Å | (4) |
| 2.79 Å | (4) |
| 6.05 Å | (3) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Near-surface Processes | |
| 23 : Subaerial aqueous alteration by non-redox-sensitive fluids (see also #47) | |
| High-? alteration and/or metamorphism | |
| 31 : Thermally altered carbonate, phosphate, and iron formations |
Type Occurrence of Scawtite
Place of Conservation of Type Material:
The Natural History Museum, London, England, 1956,384
Geological Setting of Type Material:
Contact-metamorphosed limestones and dolostones intruded by diabase.
Associated Minerals at Type Locality:
Other Language Names for Scawtite
Common Associates
Associations Based on Photo Data:
| 7 photos of Scawtite associated with Tobermorite | Ca5Si6O17 · 5H2O |
| 4 photos of Scawtite associated with Thaumasite | Ca3(SO4)[Si(OH)6](CO3) · 12H2O |
| 4 photos of Scawtite associated with Spinel | MgAl2O4 |
| 4 photos of Scawtite associated with Plombièrite | Ca5Si6O16(OH)2 · 7H2O |
| 3 photos of Scawtite associated with Gehlenite | Ca2Al[AlSiO7] |
| 3 photos of Scawtite associated with Larnite | Ca2SiO4 |
| 3 photos of Scawtite associated with Xonotlite | Ca6(Si6O17)(OH)2 |
| 2 photos of Scawtite associated with Stringhamite | CaCu(SiO4) · H2O |
| 1 photo of Scawtite associated with Spurrite | Ca5(SiO4)2(CO3) |
| 1 photo of Scawtite associated with Augite | (CaxMgyFez)(Mgy1Fez1)Si2O6 |
Related Minerals - Strunz-mindat Grouping
| 9.CK. | Adachiite | CaFe3Al6(Si5AlO18)(BO3)3(OH)3(OH) |
| 9.CK. | Magnesio-dutrowite | Na(Mg2.5Ti0.5)Al6(Si6O18)(BO3)3(OH)3O |
| 9.CK. | Darrellhenryite | Na(Al2Li)Al6(Si6O18)(BO3)3(OH)3O |
| 9.CK. | Fluor-schorl | NaFe2+3Al6(Si6O18)(BO3)3(OH)3F |
| 9.CK. | Princivalleite | Na(Mn2Al)Al6(Si6O18)(BO3)3(OH)3O |
| 9.CK. | Alumino-oxy-rossmanite | ◻Al3Al6(Si5AlO18)(BO3)3(OH)3O |
| 9.CK. | Dutrowite | Na(Fe2+2.5Ti0.5)Al6(Si6O18)(BO3)3(OH)3O |
| 9.CK. | Ferro-bosiite | NaFe3+3(Al4Fe2+2)(Si6O18)(BO3)3(OH)3O |
| 9.CK. | Bosiite | NaFe3+3(Al4Mg2)(Si6O18)(BO3)3(OH)3O |
| 9.CK. | Celleriite | ◻(Mn2+2Al)Al6(Si6O18)(BO3)3(OH)3(OH) |
| 9.CK.05 | Feruvite | CaFe2+3(Al5Mg)(Si6O18)(BO3)3(OH)3(OH) |
| 9.CK.05 | Chromium-dravite | NaMg3Cr3+6(Si6O18)(BO3)3(OH)3(OH) |
| 9.CK.05 | Fluor-rossmanite | ◻(Al2Li)Al6(Si6O18)(BO3)3(OH)3F |
| 9.CK.05 | Oxy-schorl | Na(Fe2+2Al)Al6(Si6O18)(BO3)3(OH)3O |
| 9.CK.05 | Fluor-elbaite | Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3F |
| 9.CK.05 | Dravite | NaMg3Al6(Si6O18)(BO3)3(OH)3(OH) |
| 9.CK.05 | Fluor-uvite | CaMg3(Al5Mg)(Si6O18)(BO3)3(OH)3F |
| 9.CK.05 | Foitite | ◻(Fe2+2Al)Al6(Si6O18)(BO3)3(OH)3(OH) |
| 9.CK.05 | Vanadio-oxy-dravite | NaV3(Al4Mg2)(Si6O18)(BO3)3(OH)3O |
| 9.CK.05 | Fluor-buergerite | NaFe3+3Al6(Si6O18)(BO3)3O3F |
| 9.CK.05 | 'Unnamed (F analogue of feruvite)' | CaFe2+3(Al5Mg)(Si6O18)(BO3)3(OH)3F |
| 9.CK.05 | Ertlite | NaAl3Al6(Si4B2O18)(BO3)3(OH)3O |
| 9.CK.05 | Tsilaisite | NaMn2+3Al6(Si6O18)(BO3)3(OH)3(OH) |
| 9.CK.05 | Fluor-liddicoatite | Ca(Li2Al)Al6(Si6O18)(BO3)3(OH)3F |
| 9.CK.05 | Uvite | CaMg3(Al5Mg)(Si6O18)(BO3)3(OH)3(OH) |
| 9.CK.05 | Elbaite | Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH) |
| 9.CK.05 | Fluor-tsilaisite | NaMn2+3Al6(Si6O18)(BO3)3(OH)3F |
| 9.CK.05 | Oxy-foitite | ◻(Fe2+Al2)Al6(Si6O18)(BO3)3(OH)3O |
| 9.CK.05 | Liddicoatite | Ca(Li2Al)Al6(Si6O18)(BO3)3(OH)3(OH) |
| 9.CK.05 | Vanadio-oxy-chromium-dravite | NaV3(Cr4Mg2)(Si6O18)(BO3)3(OH)3O |
| 9.CK.05 | Rossmanite | ◻(LiAl2)Al6(Si6O18)(BO3)3(OH)3(OH) |
| 9.CK.05 | Oxy-vanadium-dravite | NaV3(V4Mg2)(Si6O18)(BO3)3(OH)3O |
| 9.CK.05 | Olenite | NaAl3Al6(Si6O18)(BO3)3O3(OH) |
| 9.CK.05 | 'UM2000-64-SiO:BFeHKMg' | (K,Na)Fe3+3(Mg2Fe3+4)Si6O18(BO3)3(OH)3O |
| 9.CK.05 | Magnesio-lucchesiite | CaMg3Al6(Si6O18)(BO3)3(OH)3O |
| 9.CK.05 | Povondraite | NaFe3+3(Mg2Fe3+4)(Si6O18)(BO3)3(OH)3O |
| 9.CK.05 | Lucchesiite | CaFe2+3 Al6(Si6O18)(BO3)3(OH)3O |
| 9.CK.05 | Chromo-alumino-povondraite | NaCr3(Al4Mg2)(Si6O18)(BO3)3(OH)3O |
| 9.CK.05 | Fluor-dravite | NaMg3Al6(Si6O18)(BO3)3(OH)3F |
| 9.CK.05 | Oxy-dravite | Na(Al2Mg)(Al5Mg)(Si6O18)(BO3)3(OH)3O |
| 9.CK.05 | Oxy-chromium-dravite | NaCr3(Cr4Mg2)(Si6O18)(BO3)3(OH)3O |
| 9.CK.05 | 'Luinaite-(OH)' | NaFe2+3Al6(Si6O18)(BO3)3(OH)3(OH) |
| 9.CK.05 | Schorl | NaFe2+3Al6(Si6O18)(BO3)3(OH)3(OH) |
| 9.CK.05 | Magnesio-foitite | ◻(Mg2Al)Al6(Si6O18)(BO3)3(OH)3(OH) |
| 9.CK.05 | Maruyamaite | K(Al2Mg)(Al5Mg)(Si6O18)(BO3)3(OH)3O |
| 9.CK.10 | Abenakiite-(Ce) | Na26Ce6(Si6O18)(PO4)6(CO3)6(SO2)O |
| 9.CK.20 | Thorosteenstrupine | (Ca,Th,Mn)3Si4O11F · 6H2O |
| 9.CK.20 | Steenstrupine-(Ce) | Na14Mn2+2Fe3+2Ce6Zr(Si6O18)2(PO4)6(PO3OH)(OH)2 · 2H2O |
Other Information
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 Scawtite
mindat.org URL:
https://www.mindat.org/min-3552.html
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References for Scawtite
Reference List:
Tilley, C. E. (1930) Scawtite, a new mineral from Scawt Hill, Co. Antrim. Mineralogical Magazine and Journal of the Mineralogical Society, 22 (128) 222-224 doi:10.1180/minmag.1930.022.128.03
Murdoch, Joseph (1955) Scawtite from Crestmore, California. American Mineralogist, 40 (5-6). 505-509
McConnell, J. D. C. (1955) A chemical, optical and x-ray study of scawtite from Ballycraigy, Larne, N. Ireland. American Mineralogist, 40 (5-6) 510-514
McConnell, Duncan, Murdoch, Joseph (1958) The crystal chemistry of scawtite. American Mineralogist, 43 (5-6) 498-502
Harker, R. I. (1965) Scawtite and its synthesis. Mineralogical Magazine and Journal of the Mineralogical Society, 34 (268). 232-236 doi:10.1180/minmag.1965.034.268.18
Localities for Scawtite
Showing 31 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. (2008) |
| Greg Dainty collection. |
China | |
| Liming Zhang et al. (1991) |
| Cao Zhengmin et al. (1987) |
Cuba | |
| Chukanov (2014) |
Germany | |
| Tron et al. (1987) |
Hungary | |
| Kónya-MÁFI |
Indonesia | |
| Newman (1973) |
Ireland | |
| Bull. Soc. Franç. Minéralo. ... |
Italy | |
| Ciriotti et al. (2026) |
| Boscardin et al. (2011) |
| 50 +2 other references |
| Collections Alessandro Mattiello and ... +1 other reference |
| Mattioli et al. (2014) |
Japan | |
| Matsuyama (2001) |
| 3 +2 other references |
| Yamada (2004) | |
| Kusachi et al. (1991) +1 other reference |
New Zealand | |
| Mason (1957) +1 other reference |
| Baker et al. (1980) | |
Norway | |
| Jamtveit et al. (1997) |
Poland | |
| Łukasz Kruszewski PXRD data |
Romania | |
| Marincea +2 other references |
UK | |
| McConnell (1954) +3 other references |
| Henmi et al. (1973) |
| Tilley (1930) +2 other references |
| Agrell (1965) |
USA | |
| Anthony et al. (1995) |
| Murdoch (1955) +1 other reference |
| Murdoch (1954) +3 other references |
| Taylor (1935) +2 other references |
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Commercial Quarry, Sky Blue Hill, Crestmore quarries, Crestmore, Jurupa Valley, Riverside County, California, USA