{{Short description|Mineral}} {{Infobox mineral | name = Whewellite | boxwidth = | image = Whewellite-md82a.jpg | alt = | caption = A white Whewellite crystal from Schlema, Germany | category = Oxalate minerals | formula = CaC<sub>2</sub>O<sub>4</sub>·H<sub>2</sub>O | IMAsymbol = Whe<ref>{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}</ref> | molweight = | strunz = 10.AB.45 | dana = | system = Monoclinic | class = Prismatic (2/m) <br /><small>(same H-M symbol)</small> | symmetry = ''P2<sub>1</sub>/c'' (no. 14) | unit cell = | color = Colorless, yellowish, brownish | colour = | habit = Equant or stout prismatic crystals | twinning = ''e'' {<nowiki/>{{overline|1}}01} twin plane | cleavage = {<nowiki/>{{overline|1}}01} good, {010} imperfect, {001} indistinct, {110} indistinct | fracture = Conchoidal | tenacity = Brittle | mohs = 2.5–3 | luster = Vitreous to pearly | streak = | diaphaneity = Transparent | gravity = 2.23 | density = | polish = | opticalprop = Biaxial (+), colorless (transmitted light) | refractive = | birefringence = | pleochroism = | 2V = | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = Insoluble in water, soluble in acids | impurities = | alteration = | other = | prop1 = | prop1text = | references = <ref name="mindat">[http://www.mindat.org/min-4276.html Whewellite: mindat.org]</ref><ref>[http://www.webmineral.com/data/Whewellite.shtml Webmineral.com]</ref><ref>{{Cite web |url=http://www.handbookofmineralogy.com/pdfs/whewellite.pdf |title=''Handbook of Mineralogy'' |access-date=2011-05-15 |archive-date=2016-03-03 |archive-url=https://web.archive.org/web/20160303171459/http://www.handbookofmineralogy.com/pdfs/whewellite.pdf |url-status=dead }}</ref><ref>{{cite journal |last1=Tazzoli |first1=V. |last2=Domeneghetti |first2=M.C. |journal=American Mineralogist |volume=65 |year=1980 |pages=327–334 |title=The crystal structures of whewellite and weddellite: re-examination and comparison |url=https://pubs.geoscienceworld.org/msa/ammin/article-abstract/65/3-4/327/41138/The-crystal-structures-of-whewellite-and?redirectedFrom=fulltext |access-date=31 December 2020}}</ref> }}
'''Whewellite''' {{IPAc-en|ˈ|h|juː|ə|l|aɪ|t}} is a mineral, hydrated calcium oxalate, formula Ca C<sub>2</sub>O<sub>4</sub>·H<sub>2</sub>O.<ref>{{cite web |title= whewellite |publisher= Merriam-Webster Dictionary|url= https://www.merriam-webster.com/dictionary/whewellite |accessdate= 30 May 2024}}</ref> Because of its organic content it is thought to have an indirect biological origin; this hypothesis is supported by its presence in coal and sedimentary nodules. However, it has also been found in hydrothermal deposits where a biological source appears improbable. For this reason, it may be classed as a true mineral.
Whewellite, or at least crystalline calcium oxalate, does also arise from biological sources. Small crystals or flakes of it are sometimes found on the surfaces of some cacti, and kidney stones frequently have the same composition.
Whewellite was named after William Whewell (1794–1866), an English polymath, naturalist and scientist, professor of moral philosophy at Cambridge and inventor of the system of crystallographic indexing.<ref name="mindat"/>
==Heat decomposition== thumb|left|300px|Whewellite (calcium oxalate monohydrate) heat decomposition mass curve. The whewellite decomposes first to anhydrous calcium oxalate, then to calcium carbonate (losing carbon monoxide), and finally to calcium oxide (losing carbon dioxide). Whewellite is used as a thermogravimetric analysis standard due to its well-known decomposition temperatures and products.
== See also == * Kidney stones * List of minerals recognized by the International Mineralogical Association * List of minerals named after people
==References== {{reflist}} {{commons category|Whewellite}}
==Bibliography== *<small>Palache, P.; Berman H.; Frondel, C. (1960). "''Dana's System of Mineralogy, Volume II: Halides, Nitrates, Borates, Carbonates, Sulfates, Phosphates, Arsenates, Tungstates, Molybdates, Etc. (Seventh Edition)"'' John Wiley and Sons, Inc., New York, pp. 1099–1101.</small>
Category:Calcium minerals Category:Oxalate minerals Category:Monoclinic minerals Category:Minerals in space group 14 Category:Minerals described in 1840
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