Gaylussite

{{Infobox mineral

| name = Gaylussite

| category = Carbonate mineral

| image = Gaylussite-304155.jpg

| imagesize = 260px

| caption =

| formula = Na₂Ca(CO₃)₂·5H₂O

| IMAsymbol = Gyl{{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.CB.35

| system = Monoclinic

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

| symmetry = I2/a

| color = Colorless, white, yellow, and grey

| habit = Tabular prismatic crystals also granular

| twinning =

| cleavage = perfect [110]

| fracture = Conchoidal, brittle

| mohs = 2.5

| luster = vitreous

| refractive = nα = 1.444 nβ = 1.516 nγ = 1.523

| opticalprop = Biaxial (−)

| birefringence = δ = 0.079

| pleochroism =

| streak = white

| gravity = 1.93 – 1.99

| density =

| melt =

| fusibility =

| diagnostic =

| solubility = decomposes in water

| diaphaneity =

| other = efflorescent

| references = [http://rruff.geo.arizona.edu/doclib/hom/gaylussite.pdf Handbook of Mineralogy][http://www.mindat.org/min-1662.html Mindat][http://webmineral.com/data/Gaylussite.shtml Webmineral]

}}

Gaylussite is a carbonate mineral, a hydrated sodium calcium carbonate, formula Na₂Ca(CO₃)₂·5H₂O. It occurs as translucent, vitreous white to grey to yellow monoclinic prismatic crystals. It is an unstable mineral which dehydrates in dry air and decomposes in water.