Secondary names

Selenite

IMA Code

Gp

	Formula	Name	Family	Number min-max	Isotope mole fraction	State	Relevance
	$Ca^{2+}$	Calcium cation	element	1		constituent cation	main
	$(SO_4)^{2-}$	Sulfate anion	chemical function	1		anionic radical	main
	$H_2O$	Water	molecule	2		hydration	main

Composition comments

Slightly soluble in water. Poorly deliquescent > 99% RH at 20°C

Chemical functions

	Function	Number
	$(SO_4)^{2-}$	1
	$R-OH$	2

Chemical bonds

	Bond	Number
	$\cdot Ca^{2+} \cdot O^{-}-$	2
	$-O \dots H-$	2
	$-O-H$	2
	$\dddot - \dddot - \dddot - S \dddot - O^{-1/2}$	4

Oxides

Formula	$CaO$	$SO_{3}$	$H_{2}O$
Mass fraction (%)	32.57	46.5	20.93

Strunz

Class

sulfates - chromates - molybdates - tungstates (07)

Division

sulfates (selenates, etc.) without additional anions, with H2O (07.C)

Family

with only large cations (07.CD)

Code

07.CD.40

Dana

Major class

sulfates, chromates, selenates (VI)

Class

hydrated acid and sulfates (29)

Type

where AXO4.x(H2O) (29.06)

Group

-Gypsum- group (Dihydrates, monoclinic) (29.06.03)

Code

29.06.03.01

Phase type

crystalline

Crystal system

monoclinic

Crystal class

prismatic

Crystal class symbol

2/m (C2h)

Crystal spacegroup

C2/c

Crystal sites

Label	Nb	Type	Wp	Specie	Specie coordinence	Specie occupancy	Specie oxidation state
Ca	1			$Ca^{2+}$		1.0
S	1			$S$		1.0
O1	2			$O$		1.0
O2	2			$O$		1.0
Ow	2			$O$		1.0
H1	2			$H$		1.0
H2	2			$H$		1.0

Composition order

ordered

Refringence type

biaxial

Refringence sign

positive

Birefringence

0.0090 - 0.0100

Refraction index $n_{\alpha}$

1.519 - 1.521

Refraction index $n_{\beta}$

1.522 - 1.523

Refraction index $n_{\gamma}$

1.529 - 1.530

Dispersion V

strong

Pure color

colorless

Color

colorless, white, yellowish white, greenish white, brown

Diaphaneity

transparent to translucent

Luster

pearly

Links

• Wikipedia
• Webmineral database
• Mindat
• Handbook of Mineralogy (Min. Soc. Am)