Gypsum

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Gypsum
Mineralogical name	Gypsum, Selenite
Chemical name	Calcium sulfate dihydrate
Trivial name	{{{Trivial_Name}}}
Chemical formula	{{{chemical_Formula}}}
Other forms	Anhydrite (CaSO4) Hemihydrate (CaSO4•0.5H2O)
Crystal system	monoclinic
Crystal structure
Deliquescence humidity 20°C
Solubility (g/l) at 20°C	2.14 g/l
Density (g/cm³)	2.2-2.4 g/cm³
Molar volume	74.69 cm3/mol
Molar weight	172.17g /mol
Transparency	transparent to opaque
Cleavage	perfect
Crystal habit	{{{Crystal_Habit}}}
Twinning
Phase transition	{{{Phase_Transition}}}
Chemical behavior	{{{chemBehavior}}}
Comments	hardly soluble in water
Crystal Optics
Refractive Indices	{{{Refractive_Indices}}}
Birefringence	Δ = 0.010
Optical Orientation	{{{optical_Orientation}}}
Pleochroism
Dispersion	58°
Used Literature
{{{Literature}}}

Authors: Hans-Jürgen Schwarz , Nils Mainusch, Tim Müller
back to Sulfate

Calciumsulfate and Gipsum

Solubility properties

Figure1: Solubility of CaSO4 in water (diagram: Michael Steiger)

Figure 2:Solubility of gipsum compared with other salte (after [Stark.etal:1996]Title: Bauschädliche Salze
Author: Stark, Jochen; Stürmer, Sylvia
)

Photos of gypsum crystals and deterioration pattern caused by gypsum

On an object

• 

  Salt damage on a brick, St. Jakobi Church, Perleberg

Under the polarising microscope

• In thin section of bricks
• 

  Brick with gypsum caused damage, St. Jakobi Church, Perleberg, Germany

• 

  Brick with gypsum caused damage, St. Jakobi Church, Perleberg, Germany

• 

  Gypsum crystals between plaster layers

• Gypsum crystallized out of a solution in water on a glass slide
• 

  Calcium sulfate crystallized out of a solution in water on a glass slide

• 

  Calcium sulfate with sodium chloride of a real sample, Gypsum crystallized out of a solution in water on a glass slide

• 

  Calcium sulfate with sodium chloride of a real sample, Gypsum crystallized out of a solution in water on a glass slide

• 

  Calcium sulfate, Gypsum crystallized out of a solution in water on a glass slide

Under the Scanning Electron Microscope (SEM)

• In a SEM
• 

  Gypsum crystals in a SEM

• 

  Gypsum crystals in a SEM

• 

  Gypsum crystals in a SEM

• 

  EDX spectra of gypsum crystals in a SEM

• 

  Gypsum crystals in a SEM

• 

  Gypsum crystals in a SEM

• 

  Gypsum crystals in a SEM

• 

  EDX spectra of gypsum crystals in a SEM

Literatur

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A phase is a physically distinctive form of matter and is characterized by having relatively uniform chemical and physical properties.

Scanning Electron Microscope