Epsomite

{{Infobox mineral

| name = Epsomite

| category = Sulfate mineral

| boxwidth =

| boxbgcolor =

| image = Epsomita 01.jpg

| imagesize =

| caption = Epsomite formation from a Calatayud, Spain cave

| formula = {{chem2|MgSO4*7H2O}}

| IMAsymbol = Esm{{cite magazine |last=Warr |first=L.N. |year=2021 |title=IMA–CNMNC approved mineral symbols |magazine=Mineralogical Magazine |volume=85 |issue=3 |pages=291–320 |doi=10.1180/mgm.2021.43 |doi-access=free |bibcode=2021MinM...85..291W |s2cid=235729616 }}

| strunz = 7.CB.40

| dana = 29.6.11.1

| system = Orthorhombic

| class = Disphenoidal (222)
H-M symbol: (2 2 2)

| symmetry = P2₁2₁2₁

| unit cell = {{mvar|a}} = 11.86, {{mvar|b}} = 11.99
{{mvar|c}} = 6.858 [Å]; {{nobr|{{mvar|Z}} {{=}} 4}}

| color = White, grey, colorless, or pink, greenish

| colour =

| habit = Acicular to fibrous encrustations

| twinning = Rarely observed on {110}

| cleavage = {010} perfect {101} distinct

| fracture = Conchoidal

| tenacity =

| mohs = 2

| luster = Vitreous, silky when fibrous

| streak =

| diaphaneity = Transparent to translucent

| gravity = 1.67–1.68

| density =

| polish =

| opticalprop = Biaxial (−)

| refractive = {{mvar|n}}{{sub|{{mvar|α}}}} = 1.433 {{mvar|n}}{{sub|{{mvar|β}}}} = 1.455 {{mvar|n}}{{sub|{{mvar|γ}}}} = 1.461

| birefringence = {{mvar|δ}} = 0.028

| pleochroism =

| 2V = Measured: 52°

| dispersion =

| extinction =

| length fast/slow =

| fluorescence=

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| melt =

| fusibility =

| diagnostic =

| solubility = In water

| other =

| alteration = Dehydrates in dry air

| references = {{cite web |title=Epsomite |website = Web Mineral (webmineral.com) |url=http://webmineral.com/data/Epsomite.shtml }}{{cite web |title = Epsomite |website = Mindat.org |url = http://www.mindat.org/min-1393.html }}{{cite report |title = Epsomite |series = Handbook of Mineralogy |via = Dept. Geology, University of Arizona |url = http://rruff.geo.arizona.edu/doclib/hom/epsomite.pdf }}

}}

Epsomite, Epsom salt, or magnesium sulfate heptahydrate, is a hydrous magnesium sulfate mineral with formula {{chem2|MgSO4*7H2O}}.

Physical properties

Epsomite crystallizes in the orthorhombic system. The normal form is as massive encrustations, while acicular or fibrous crystals are rarely found. It is colorless to white with tints of yellow, green and pink. It is a soft mineral with variable Mohs hardness around 2.0~2.5, and it has a low specific gravity {{nobr| of 1.67.}}{{cite web |title=Epsomite |url=http://mineral.galleries.com/minerals/sulfates/epsomite/epsomite.htm |url-status=dead |archive-url=https://web.archive.org/web/20060317160728/http://mineral.galleries.com/minerals/sulfates/epsomite/epsomite.htm |archive-date=2006-03-17 |website=Mineral galleries (mineral.galleries.com) |department=Sulfates |df=dmy-all}}

It is readily soluble in water, and absorbs water from the air. It converts to hexahydrate with the loss of one water molecule and a switch to monoclinic structure.

The epsomite group includes solid solution series with morenosite ({{chem|Ni|S|O|4}}·{{chem|7 H|2|O}}) and goslarite ({{chem|Zn|S|O|4}}·{{chem|7 H|2|O}}).{{Clarification needed|date=May 2024}}

Etymology

It was first systematically described in 1806 for an occurrence near Epsom, Surrey, England, after which it was named. It has been also referred to as "cave cotton" when in its fibrous form.

Occurrence

Epsomite forms as encrustations or efflorescences on limestone cavern walls and mine timbers and walls, rarely as volcanic fumarole deposits, and as rare beds in evaporite layers such as those found in certain bodies of salt water.{{cite book |title=McGraw-Hill Encyclopedia of Science & Technology |edition=10th |year=2007 |place=New York, NY |publisher=McGraw-Hill |isbn=9780071441438 |oclc=84152915}} It occurs in association with melanterite, gypsum, halotrichite, pickeringite, alunogen, rozenite, and mirabilite.

Naturally occurring epsomite in caverns can potentially produce particulates of inhalable size, and may contain significant amounts of toxic impurities.{{Cite journal |last1=Giordani |first1=Matteo |last2=Meli |first2=Maria Assunta |last3=Roselli |first3=Carla |last4=Betti |first4=Michele |last5=Peruzzi |first5=Fabio |last6=Taussi |first6=Marco |last7=Valentini |first7=Laura |last8=Fagiolino |first8=Ivan |last9=Mattioli |first9=Michele |date=April 2022 |title=Could soluble minerals be hazardous to human health? Evidence from fibrous epsomite |url=https://linkinghub.elsevier.com/retrieve/pii/S0013935121018806 |journal=Environmental Research |language=en |volume=206 |pages=112579 |doi=10.1016/j.envres.2021.112579|pmid=34968437 |bibcode=2022ER....20612579G |hdl=11576/2693349 |hdl-access=free }}

Uses

Epsom salt is commonly sold as the main ingredient in bath salt, with additives such as glycerin (used as a humectant) and fragrances. The purpose of bath salts is mostly to make the bathing experience more enjoyable and serve as a vehicle for cosmetics, though they are said to improve cleaning and aid in exfoliation.{{cite book |last=Browning |first=Marie |year=1999 |title=Natural Soapmaking |edition=1st ppb |place=New York, NY |publisher=Sterling |isbn=0-8069-6289-5 |oclc=42598586 |url=https://www.worldcat.org/oclc/42598586}}

Research on topical magnesium (for example Epsom salt baths) is very limited.{{cite web |last1=Rath |first1=Linda |title=Why take an epsom salts bath? |series = A-to-Z guides |website=WebMD (webmd.com) |lang=en-US |url=https://www.webmd.com/a-to-z-guides/epsom-salt-bath }} The trade organization 'Epsom Salt Council' recommends bathing 2 or 3 times/week, using {{cvt|500-600|g|oz}} Epsom salts each time.{{cite report |title = Report on absorption of magnesium sulfate |publisher = Epsom Salt Council |date = October 2015 |type = commercial / promotional |url = https://www.epsomsaltcouncil.org/wp-content/uploads/2015/10/report_on_absorption_of_magnesium_sulfate.pdf |via = epsomsaltcouncil.org }}