Epsomite, Epsom salt, or magnesium sulfate heptahydrate, is a hydrous magnesium sulfate mineral with formula .
Physical properties
Epsomite crystallizes in the
orthorhombic system. The normal form is as massive encrustations, while acicular or fibrous crystals are rarely found. It is colorless to white with tints of yellow, green and pink. It is a soft mineral with variable
Mohs hardness around 2.0~2.5, and it has a low
specific gravity
It is readily soluble in water, and absorbs water from the air. It converts to hexahydrate with the loss of one water molecule and a switch to monoclinic structure.
The epsomite group includes solid solution series with morenosite (·) and goslarite (·).
Etymology
It was first systematically described in 1806 for an occurrence near
Epsom,
Surrey,
England, after which it was named.
It has been also referred to as "cave cotton" when in its fibrous form.
Occurrence
Epsomite forms as
or
on
limestone cavern walls and mine timbers and walls, rarely as
volcanic fumarole deposits, and as rare beds in
evaporite layers such as those found in certain bodies of salt water.
It occurs in association with
melanterite,
gypsum,
halotrichite,
pickeringite,
alunogen,
rozenite, and
mirabilite.
[
]
Naturally occurring epsomite in caverns can potentially produce particulates of inhalable size, and may contain significant amounts of toxic impurities.
Uses
Epsom salt is commonly sold as the main ingredient in Bath salts, with additives such as glycerin (used as a humectant) and fragrances. The purpose of bath salts is mostly to make the bathing experience more enjoyable and serve as a vehicle for cosmetics, though they are said to improve cleaning and aid in exfoliation.
Research on topical magnesium (for example Epsom salt baths) is very limited.
Gallery
See also
