Struvite

struvite

newberyite

hannayite

brushite

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Formula: (NH4)Mg(PO4).6H2O
Hydrated normal phosphate, struvite group
Crystal System: Orthorhombic
Specific gravity: 1.711 measured, 1.705 calculated
Hardness: 1½ to 2
Streak: White
Colour: Colourless, white (dehydrated), yellow or brownish, light grey; colourless in transmitted light
Solubility: Readily soluble in acids, very slightly soluble in water

Environments

Cave deposits

Struvite is typically formed in bird or bat guano in caves and surface deposits, associated with newberyite, hannayite, brushite and stercorite (HOM). It is found as a product of organic decay in putrescent matter, canned foods or other organic matter (Mindat, Webmin).

Localities

Near Dawson, Yukon, Canada, struvite from the decaying tooth of a mammoth occurs with newberyite and magnesite (Dana).

At the type locality, St Nikolai church, Hamburg, Germany, struvite was found in Medieval sewers (Mindat) in a bed of peat underlying deposits of organic matter (Dana).

At Paoha Island, Mono Lake, Mono county, California, USA, newberyite pseudomorphs after struvite have been found (KL p197).

Alteration

Mixtures of the commonly associated minerals hannayite, schertelite, bobierrite, newberyite and struvite may be formed by reaction of magnesium with concentrated ammonium phosphate solutions of the guano deposit, followed by alterations in the course of leaching and aeration. In laboratory preparations, hannayite and schertelite precipitate rapidly from concentrated solutions of ammonium phosphate over the pH range 3.5 to 6 (acid) and the temperature range 25 to 100oC. Newberyite or struvite, depending on the pH, is formed at lower concentrations of ammonium phosphate. When either newberyite or struvite is placed in a saturated solution of monoammonium phosphate, it is replaced by hannayite, which then alters to schertelite in a few days (AM 48.635-641).

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