Celestine

sulphate

calcite

Formula: Sr(SO4)
Sulphate
Specific gravity: 3.9 to 4.0
Hardness: 3 to 3½
Streak: White
Colour: Colourless, white, blue, reddish, greenish, brownish
Solubility: Slightly soluble in hydrochloric, sulphuric and nitric acid
Environments:

Sedimentary environments
Hydrothermal environments
Basaltic cavities

Celestine is a strontium mineral that may be directly deposited from seawater, or precipitated from surface waters percolating through veins and fissures. It also forms occasionally in hydrothermal deposits. It is common as a minor constituent of evaporites and it is found disseminated through limestone, shale, dolomite and sandstone. It is also found occasionally in vesicles in volcanic rocks (Dana).
Common associates include calcite, dolomite, gypsum, halite, sulphur and fluorite. Celestine occurs either as a primary precipitate from aqueous solutions or, more usually, by the interaction of gypsum or anhydrite with strontium-rich waters. Beds of celestine are therefore commonly found immediately above or below gypsum or anhydrite deposits.

At Aust Cliff, Gloucestershire, England, UK, celestine occurs in mudstone (RES p157).

At Lilliput, near Yate, Gloucestershire, England, UK, celestine variety barytocelestine occurs with calcite and galena (RES p167).

At the Harry Stoke mine, near Filton, South Gloucestershire, England, UK, celestine occurs with calcite and quartz variety amethyst (RES p168).

At the Hampstead Farm quarry, Chipping Sodbury, South Gloucestershire, England, UK, celestine occurs with sphalerite, galena, pyrite and calcite in a limestone breccia (RES p171).

At the Barrow upon Soar gypsum mine, Leicestershire, England, UK, celestine occurs with calcite filling fractures in a septarian nodule (RES p209).

At the Blaby brick kiln quarry, Leicestershire, England, UK, celestine occurs in mudstone (RES p211).

At the Clayton adit, Ecton mine, Staffordshire, England, UK, celestine occurs on calcite with minor millerite (RES p308).

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