Nesquehonite

{{Short description|Trihydrated magnesium carbonate}}

{{Infobox mineral

| name = Nesquehonite

| boxwidth =

| boxbgcolor =

| image =

| imagesize =

| alt =

| caption =

| category = Carbonates

| formula = {{Format molecular formula|MgCO3·3H2O}}

| IMAsymbol = Nes{{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 = 5.CA.05

| dana = 13.1.5.1

| system = Monoclinic

| class =

| symmetry = P2₁/m

| unit cell = a=7.705 Å, b=5.367 Å, c=12.121 Å, β=90.451°

| colour = Colourless

| habit =

| twinning =

| cleavage = Perfect

| fracture =

| tenacity =

| toughness =

| mohs = 2.5

| luster = Vitreous (if fresh)

| streak =

| diaphaneity = Translucent

| gravity = 1.824-1.854

| density = 1.6

| polish =

| opticalprop =

| refractive =

| birefringence = 0.114

| pleochroism =

| 2V =

| dispersion =

| extinction =

| length fast/slow =

| fluorescence =

| absorption =

| melt =

| Curie temp =

| fusibility =

| diagnostic =

| solubility =

| impurities =

| alteration =

}}

Nesquehonite is a mineral of magnesium carbonate ({{chem|Mg|C|O|3}}). It represents the trihydrate of magnesium carbonate, and has the total formula {{Format molecular formula|MgCO3·3H2O}}.{{Cite web|title=Nesquehonite: Mineral information, data and localities|url=https://www.mindat.org/min-2885.html|access-date=2024-12-04}}

It was described in 1890 by F. A. Genth and S. L. Penfield and is named after its type locality of Nesquehoning, Pennsylvania, where it was sampled from a coal mine. Nesquehonite can form from the related pentahydrate Lansfordite by dehydration at room temperature.