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| Dickite | |
|---|---|
 | |
| General | |
| Category | Phyllosilicates Kaolinite-serpentine group |
| Formula (repeating unit) | Al2Si2O5(OH)4 |
| IMA symbol | Dck[1] |
| Strunz classification | 9.ED.05 |
| Dana classification | 71.01.01.01 |
| Crystal system | Monoclinic |
| Crystal class | Domatic (m) (same H-M symbol) |
| Space group | Cc |
| Unit cell | a = 5.150, b = 8.940 c = 14.424 [Å]; β = 96.8°; Z = 4 |
| Identification | |
| Color | White, with coloration from impurities |
| Crystal habit | Pseudohexagonal crystals, aggregates of platelets and compact massive |
| Cleavage | Perfect on {001} |
| Tenacity | Flexible but inelastic |
| Mohs scale hardness | 1.5–2 |
| Luster | Satiny to pearly |
| Streak | White |
| Diaphaneity | Transparent |
| Specific gravity | 2.6 |
| Optical properties | Biaxial (+) |
| Refractive index | nα = 1.561 – 1.564 nβ = 1.561 – 1.566 nγ = 1.566 – 1.570 |
| Birefringence | δ = 0.005 – 0.006 |
| 2V angle | Measured: 50° to 80° |
| References | [2][3][4][5][6][7][8][9][10][11][12] |
Dickite (Al2Si2O5(OH)4) is a phyllosilicate clay mineral named after the metallurgical chemist Allan Brugh Dick, who first described it. It is chemically composed of 20.90% aluminium, 21.76% silicon, 1.56% hydrogen and 55.78% oxygen. It has the same composition as kaolinite, nacrite, and halloysite, but with a different crystal structure (polymorph). Dickite sometimes contains impurities such as titanium, iron, magnesium, calcium, sodium and potassium.[3]
Dickite occurs with other clays and requires x-ray diffraction for its positive identification. Dickite is an important alteration indicator[clarification needed] in hydrothermal systems as well as occurring in soils and shales.
Dickite's type location is in Pant-y-Gaseg, Amlwch, Isle of Anglesey, Wales, United Kingdom, where it was first described in 1888.[3] Dickite appears in locations with similar qualities and is found in China, Jamaica, France, Germany, United Kingdom, United States, Italy, Belgium and Canada.[12]
- ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
- ^ Anthony JW, Bideaux RA, Bladh KW, et al. (1995). "Dickite" (PDF). Handbook of mineralogy. Tucson, Ariz.: Mineral Data Publishing. ISBN 9780962209734. OCLC 20759166.
- ^ a b c "Dickite: Mineral information, data and localities". MinDat.org. Retrieved 27 Mar 2019.
- ^ "Dickite Mineral Data". webmineral.com. Retrieved 27 Mar 2019.
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Mainwas invoked but never defined (see the help page). - ^ a b Brindley GW, Porter AR (1978). "Occurrence of dickite in Jamaica-ordered and disordered varieties". Am. Mineral. 63 (5–6): 554–562. S2CID 41328124.