Whewellite

{{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 = CaC₂O₄·H₂O

| IMAsymbol = Whe{{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}}

| molweight =

| strunz = 10.AB.45

| dana =

| system = Monoclinic

| class = Prismatic (2/m)
(same H-M symbol)

| symmetry = P2₁/c (no. 14)

| unit cell =

| color = Colorless, yellowish, brownish

| colour =

| habit = Equant or stout prismatic crystals

| twinning = e {{{overline|1}}01} twin plane

| cleavage = {{{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)

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| solubility = Insoluble in water, soluble in acids

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| references = [http://www.mindat.org/min-4276.html Whewellite: mindat.org][http://www.webmineral.com/data/Whewellite.shtml Webmineral.com][http://www.handbookofmineralogy.com/pdfs/whewellite.pdf Handbook of Mineralogy]{{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}}

}}

Whewellite {{IPAc-en|ˈ|h|juː|ə|l|aɪ|t}} is a mineral, hydrated calcium oxalate, formula Ca C₂O₄·H₂O.{{cite web |title= whewellite |publisher= Merriam-Webster Dictionary|url= https://www.merriam-webster.com/dictionary/whewellite |accessdate= 30 May 2024}} 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.