Howlite
A valid IMA mineral species - grandfathered
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About Howlite
Henry How
Formula:
Ca2B5SiO9(OH)5
Colour:
White, colorless, brown
Lustre:
Sub-Vitreous
Hardness:
6½
Specific Gravity:
2.62
Crystal System:
Monoclinic
Name:
First described as silicoborocalcite by Henry How (11 July 1828, London, England - 28 September 1879, Windsor, Nova Scotia) chemist, geologist, and mineralogist. Professor of Natural History and Chemistry at King's College, Windsor, Nova Scotia, Canada. Renamed shortly afterwards to howlite by James Dwight Dana.
Type Locality:
Usually compact earthy masses and very rarely in crystals. The earthy material gives a "hardness" of 3.5 but this is just the hardness of separating the grains. The crystals give a hardness of 6.5 (see: http://www.mindat.org/mesg-7-226293.html)
Visit gemdat.org for gemological information about Howlite.
Visit gemdat.org for gemological information about Howlite.Unique Identifiers
Mindat ID:
1936
Long-form identifier:
mindat:1:1:1936:7
GUID
(UUID V4):
(UUID V4):
b2a0bbe6-6ad7-4434-9a42-73c10b2d6c1a
IMA Classification of Howlite
Approved, 'Grandfathered' (first described prior to 1959)
IMA Formula:
Ca2SiB5O9(OH)5
First published:
1868
Classification of Howlite
6.CB.20
6 : BORATES
C : Triborates
B : Ino-triborates
6 : BORATES
C : Triborates
B : Ino-triborates
25.3.5.1
25 : ANHYDROUS BORATES CONTAINING HYDROXYL OR HALOGEN
3 : Triborates
25 : ANHYDROUS BORATES CONTAINING HYDROXYL OR HALOGEN
3 : Triborates
17.5.12
17 : Silicates Containing other Anions
5 : Borosilicates
17 : Silicates Containing other Anions
5 : Borosilicates
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 |
|---|---|---|
| How | 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 Howlite
Pronunciation:
| Play | Recorded by | Country |
|---|---|---|
| Jolyon Ralph | United Kingdom |
Physical Properties of Howlite
Sub-Vitreous
Transparency:
Transparent
Colour:
White, colorless, brown
Streak:
White
Hardness:
6½ on Mohs scale
Comment:
crystals 6.5; massive 3.5
Comment:
Even and smooth in porcelaneous types.
Density:
2.62 g/cm3 (Measured) 2.61 g/cm3 (Calculated)
Optical Data of Howlite
Type:
Biaxial (-)
RI values:
nα = 1.583 - 1.586 nβ = 1.596 - 1.598 nγ = 1.600
2V:
Measured: 60° to 90°, Calculated: 88°
Max Birefringence:
δ = 0.017
Image shows birefringence interference colour range (at 30µm thickness)
and does not take into account mineral colouration.
and does not take into account mineral colouration.
Surface Relief:
Moderate
Dispersion:
none
Optical Extinction:
X = b; Z ∧ c ≃ 51°.
Chemistry of Howlite
Mindat Formula:
Ca2B5SiO9(OH)5
Common Impurities:
Na,K
Crystallography of Howlite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
P21/b
Setting:
P21/c
Cell Parameters:
a = 12.820(3) Å, b = 9.351(1) Å, c = 8.608(2) Å
β = 104.84(2)°
β = 104.84(2)°
Ratio:
a:b:c = 1.371 : 1 : 0.921
Unit Cell V:
997.5 ų
Z:
4
Morphology:
Flattened prismatic with pointed terminations. Elongated on [010] or [001].
Compact nodular masses, internally dense and structureless. Chalk-like, earthy, scaly, slaty structured.
Compact nodular masses, internally dense and structureless. Chalk-like, earthy, scaly, slaty structured.
Comment:
Cell data from Griffen (1988).
Crystal Structure
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Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
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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) |
|---|---|---|---|---|---|---|---|
| 0000202 | Howlite | Finney J J, Kumbasar I, Konnert J A, Clark J R (1970) Crystal structure of the calcium silicoborate, howlite American Mineralogist 55 716-728 |  | 1970 | 0 | 293 | |
| 0001197 | Howlite | Griffen D T (1988) Howlite, Ca2SiB5O9(OH)5: Structure refinement and hydrogen bonding American Mineralogist 73 1138-1144 | | 1988 | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Image Loading
Radiation - Copper Kα
Data courtesy of RRUFF project at University of Arizona, used with permission.
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 6.2 Å | (100) |
| 3.10 Å | (90) |
| 3.90 Å | (80) |
| 2.04 Å | (70) |
| 2.07 Å | (50) |
| 1.794 Å | (50) |
| 12.4 Å | (40) |
Comments:
Sterling Borax mine, California, USA. Data from Murdoch (1957).
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Near-surface Processes | |
| 25 : Evaporites (prebiotic) |
Geological Setting:
In borate deposits. The common associates include those at Piskanya deposit (studenitsite is not a common species)
Type Occurrence of Howlite
General Appearance of Type Material:
Nodules embedded in anhydrite or gypsum.
Place of Conservation of Type Material:
No designated type material.
Geological Setting of Type Material:
Gypsum and anhydrite deposit.
Associated Minerals at Type Locality:
Reference:
How, H. (1868) Contributions to the mineralogy of Nova Scotia. III. Borates and other minerals in anhydrite and gypsum. Silicoborocalcite, a new mineral. Philosophical Magazine: 35, (4th Ser.), 32-41, 218.
Synonyms of Howlite
Other Language Names for Howlite
Common Associates
Related Minerals - Strunz-mindat Grouping
| 6.CB.10 | Colemanite | Ca[B3O4(OH)3] · H2O |
| 6.CB.15 | Hydroboracite | CaMg[B3O4(OH)3]2 · 3H2O |
| 6.CB.25 | Jarandolite | Ca[B3O4(OH)3] |
Fluorescence of Howlite
May fluoresce orange or bluish white with SW or LW.
Other Information
IR Spectrum:
Piskanya material [cm-1]: 3460, 3492, 3404, 3212, 1455, 1435, 1410, 1379w, 1359, 1324, 1223, 1163, 1136, 1104, 1055sh, 1014s, 959s, 915s, 906s, 875, 831s, 761, 775, 750w, 707w, 682, 617, 595, 563w, 551w, 527, 511w, 466, 451
Thermal Behaviour:
Before the blowpipe, decrepitates strongly, and fuses readily to a clear colourless bead, making the inner flame green. In a closed tube it decrepitates and gives much water.
Notes:
Readily soluble in dilute acids. Gelatinous silica results from the reaction upon evaporation. A minute quantity with a drop of dilute HCl gives the boracic-acid test with tumeric paper.
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 Howlite
mindat.org URL:
https://www.mindat.org/min-1936.html
Please feel free to link to this page.
Please feel free to link to this page.
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External Links:
Mineral Dealers:
References for Howlite
Reference List:
Giles, W. B. (1903) Bakerite (a new borosilicate of calcium) and howlite from California. Mineralogical Magazine and Journal of the Mineralogical Society, 13 (62) 353-355 doi:10.1180/minmag.1903.013.62.12
Murdoch, Joseph (1957) Crystallography and x-ray measurements of howlite from California. American Mineralogist, 42 (7-8) 521-524
Finney, J. J., Kumbasar, Isik, Clark, Joan R. (1969) Crystal structure of howlite, Ca2SiB5O9(OH)5. Die Naturwissenschaften, 56 (1) 33-34 doi:10.1007/bf00599589
Finney, J. J., Kumbasar, Isik, Konnert, Judith A., Clark, Joan R. (1970) Crystal structure of the calcium silicoborate howlite. American Mineralogist, 55 (5-6) 716-728
Papezik, V. S., Fong, C. C. K. (1975) Howlite and ulexite from the Carboniferous gypsum and anhydrite beds in western Newfoundland. The Canadian Mineralogist, 13 (4) 370-376
Griffen, Dana T. (1988) Howlite, Ca2SiB5O9(OH)5: Structure refinement and hydrogen bonding. American Mineralogist, 73 (9-10) 1138-1144
Grice, J. D., Gault, R. A., Van Velthuizen, J. (2005) Borate minerals of the Penobsquis and Millstream deposits, southern New Brunswick, Canada. The Canadian Mineralogist, 43 (5) 1469-1487 doi:10.2113/gscanmin.43.5.1469
Localities for Howlite
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.
Bolivia | |
| Bentz (2017) |
Canada | |
| Roulston et al. (1981) |
| Burns et al. (1992) |
| Papezik et al. (1975) |
| Papezik et al. (1975) | |
| Ronnie Van Dommelen collection |
| Papezik et al. (1975) |
| How (1868) +2 other references |
| Papezik et al. (1975) +2 other references |
| Joyce et al. (1993) |
Germany | |
| Kühn et al. (1962) +3 other references |
| Siemroth (2008) |
Mexico | |
| stratigraphy et al. (4) +2 other references |
| Verley et al. (2011) | |
| Verley et al. (2011) | |
| Verley et al. (2011) | |
| stratigraphy et al. (4) +1 other reference |
| Garrett (1998) |
Serbia | |
| Econ Geol (1992) |
| Econ Geol (1992) | |
| Canadian Mineralogist Vol. 13 (1975) +1 other reference | |
Slovakia | |
| Koděra (1986) |
Turkey | |
| Helvaci +2 other references |
| A Summary and Geological Comparison. ... +2 other references |
| A Summary and Geological Comparison. ... +3 other references |
UK | |
| Smith et al. (2014) |
| Smith et al. (2014) |
| Smith et al. (2014) | |
| Kemp et al. (2016) | |
USA | |
| Palache et al. (1951) |
| Chandler (1996) |
| www.mineralsocal.org |
| Van Nostrand Reinholt Press: 510. +4 other references | |
| Gale (1946) +1 other reference | |
| Palache et al. (1951) |
| Rocks & Minerals: 11: 156. +9 other references |
| Murdoch et al. (1966) |
| Giles (1903) +1 other reference |
| Palache et al. (1951) | |
| Van Nostrand Reinholt Press: 510. +2 other references |
| Van Nostrand Reinholt Press: 510. +2 other references |
| Van Nostrand Reinholt Press: 511. +3 other references |
| Palache et al. (1951) |
Quick NavTopAbout HowliteUnique IdentifiersIMA Classification Classification Mineral SymbolsPronunciation Physical Properties Optical Data Chemistry Crystallography Crystal StructureX-Ray Powder DiffractionGeological EnvironmentType Occurrence SynonymsOther LanguagesCommon AssociatesStrunz-MindatFluorescence Other InformationInternet Links References Localities Locality List
Bras D'Or Lake howlite locality, Iona, Victoria Co., Nova Scotia, Canada