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Yellow sassolite
CategoryBorate mineral
(repeating unit)
IMA symbolSso[1]
Strunz classification6.AA.05
Crystal systemTriclinic
Crystal classPinacoidal (1)
(same H-M symbol)
Space groupP1
Unit cella = 7.02 Å, b = 7.06 Å
c = 6.59 Å; α = 103.65°
β = 101.11°, γ = 59.98°; Z = 4
ColourWhite to gray, may be pale yellow from included sulfur or pale brown from included iron oxides; colourless in transmitted light
Crystal habitAs scaly pseudohexagonal crystals; ncrustations; platy; tabular; may be stalactitic
TwinningAround [001] as twin axis, common
CleavagePerfect on {001}, micaceous
Mohs scale hardness1
LustreVitreous to pearly
Specific gravity1.46-1.50
Optical propertiesBiaxial (-)
Refractive indexnα = 1.340 nβ = 1.456 nγ = 1.459
Birefringenceδ = 0.119
2V angleMeasured: 5°, Calculated: 16°
SolubilitySoluble in water

Sassolite is a borate mineral, specifically the mineral form of boric acid. It is usually white to gray, and colourless in transmitted light. It can also take on a yellow colour from sulfur impurities, or brown from iron oxides.[2]

History and occurrence[edit]

Its mineral form was first described in 1800, and was named after Sasso Pisano, Castelnuovo Val di Cecina, Pisa Province, Tuscany, Italy where it was found.[4] The mineral may be found in lagoons throughout Tuscany and Sasso.[3] It is also found in the Lipari Islands and the US state of Nevada. It occurs in volcanic fumaroles and hot springs, deposited from steam, as well as in bedded sedimentary evaporite deposits.[2]

See also[edit]


  1. ^ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi:10.1180/mgm.2021.43. S2CID 235729616.
  2. ^ a b c Handbook of Mineralogy
  3. ^ a b
  4. ^ a b MinDAT

External links[edit]

Media related to Sassolite at Wikimedia Commons