Smithsonite,also known aszinc spar,is the mineral form ofzinc carbonate(ZnCO3). Historically, smithsonite was identified withhemimorphitebefore it was realized that they were two different minerals. The two minerals are very similar in appearance and the termcalaminehas been used for both, leading to some confusion. The distinct mineral smithsonite was named in 1832 byFrançois Sulpice Beudantin honor ofEnglishchemistandmineralogistJames Smithson(c. 1765–1829), who first identified the mineral in 1802.[3][5]
| Smithsonite | |
|---|---|
 | |
| General | |
| Category | Carbonate mineral |
| Formula (repeating unit) | ZnCO3 |
| IMA symbol | Smt[1] |
| Strunz classification | 5.AB.05 |
| Crystal system | Trigonal |
| Crystal class | Hexagonal scalenohedral (3m) H-M symbol:(32/m) |
| Space group | R3c |
| Unit cell | a = 4.6526(7) c = 15.0257(22) [Å]; Z = 6 |
| Identification | |
| Color | White, grey, yellow, green to apple-green, blue, pink, purple, bluish grey, and brown |
| Crystal habit | Uncommon as crystals, typically botryoidal, reniform, spherulitic; stalactitic, earthy, compact massive |
| Twinning | None observed |
| Cleavage | Perfect on [1011] |
| Fracture | Uneven, sub-conchoidal |
| Tenacity | Brittle |
| Mohs scalehardness | 4.5 |
| Luster | Vitreous, may be pearly |
| Streak | White |
| Diaphaneity | Translucent |
| Specific gravity | 4.4–4.5 |
| Optical properties | Uniaxial (−) |
| Refractive index | nω= 1.842 – 1.850 nε= 1.619 – 1.623 |
| Birefringence | δ = 0.223 – 0.227 |
| Ultravioletfluorescence | May fluoresce pale green or pale blue under UV |
| References | [2][3][4] |
Smithsonite is a variably coloredtrigonalmineral which only rarely is found in well formed crystals. The typical habit is as earthybotryoidalmasses. It has aMohs hardnessof 4.5 and aspecific gravityof 4.4 to 4.5.
Smithsonite occurs as a secondary mineral in theweatheringoroxidationzone of zinc-bearingoredeposits. It sometimes occurs as replacement bodies incarbonate rocksand as such may constitute zinc ore. It commonly occurs in association with hemimorphite,willemite,hydrozincite,cerussite,malachite,azurite,aurichalciteandanglesite.It forms two limitedsolid solutionseries, with substitution ofmanganeseleading torhodochrosite,and withiron,leading tosiderite.[4]A variety rich incadmium,which gives it a bright yellow color, is sometimes calledturkey fat ore. The cause of colour is the presence of greenockite inclusions.[2]
Gallery
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Crystals of smithsonite: Ojuela Mine, Mapimi, Mun. de Mapimi, Durango, Mexico -
Crystals of pink cobaltoan smithsonite on matrix -
Apple-green cuprian smithsonite crystals. A second generation ofdrusysmithsonite was deposited in the crevasses between the larger growth. -
Crystals of slightly pink cobaltoan smithsonite, Tsumeb, 6.8 × 4.6 × 3.7 cm -
Blue smithsonite from the Kelly Mine in New Mexico
See also
editReferences
edit- ^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.S2CID235729616.
- ^abSmithsonite: Smithsonite mineral information and data from Mindat
- ^abSmithsonite mineral data from Webmineral
- ^abAnthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C. (2005)."Smithsonite"(PDF).Handbook of Mineralogy.Mineral Data Publishing.Retrieved14 March2022.
- ^"Smithsonite at the National Museum of Natural History".Smithsonian Institution.Retrieved8 December2010.
Bibliography
edit- Tom Hughes, Suzanne Liebetrau, and Gloria Staebler, eds. (2010).Smithsonite: Think Zinc!Denver, CO: LithographieISBN978-0-9790998-6-1.
- Ewing, Heather (2007).The Lost World of James Smithson: Science, Revolution, and the Birth of the Smithsonian.London and New York: BloomsburyISBN978-1-59691-029-4
External links
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