Crystals of struvite from dog urine
|Color||Colourless, white (dehydrated), yellow or brownish, light gray|
|Crystal habit||Euhedral to platey|
|Crystal system||Orthorhombic - Pyramidal|
|Mohs scale hardness||1.5–2|
|Luster||Vitreous to dull|
|Diaphaneity||Transparent to translucent|
|Optical properties||Biaxial (+) 2V Measured: 37°|
|Refractive index||nα = 1.495 nβ = 1.496 nγ = 1.504|
|Birefringence||δ = 0.009|
|Solubility||Slightly soluble, dehydrates in dry, warm air|
|Other characteristics||Pyroelectric and piezoelectric|
Struvite (magnesium ammonium phosphate) is a phosphate mineral with formula: NH4MgPO4·6H2O. Struvite crystallizes in the orthorhombic system as white to yellowish or brownish-white pyramidal crystals or in platey mica-like forms. It is a soft mineral with Mohs hardness of 1.5 to 2 and has a low specific gravity of 1.7. It is sparingly soluble in neutral and alkaline conditions, but readily soluble in acid.
Struvite urinary stones and crystals form readily in the urine of animals and humans that are infected with ammonia-producing organisms. They are potentiated by alkaline urine and high magnesium excretion (high magnesium/plant-based diets). They also are potentiated by a specific urinary protein, in domestic cats.
Struvite is occasionally found in canned seafood, where its appearance is that of small glass slivers, objectionable to consumers for aesthetic reasons but of no health consequence.
Use of struvite as an agricultural fertilizer was in fact first described in 1857.
Struvite kidney stones 
Struvite precipitates in alkaline urine, forming stones. Struvite is the most common mineral found in urinary tract stones in dogs, and is found also in urinary tract stones of cats and humans. Struvite stones are potentiated by bacterial infection that hydrolyzes urea to ammonium and raises urine pH to neutral or alkaline values. Urea-splitting organisms include Proteus, Pseudomonas, Klebsiella, Staphylococcus, and Mycoplasma.
Even in the absence of infection, accumulation of struvite crystals in the urinary bladder is a problem frequently seen in housecats, with symptoms including difficulty urinating (which may be mistaken for constipation) or blood in the urine (hematuria). The protein cauxin, a protein excreted in large amounts in cat urine that acts to produce a feline pheromone, has recently been found to cause nucleation of struvite crystals in a model system containing the ions necessary to form struvite. This may explain some of the excess struvite production in domestic cats. In the past, surgery has been required to remove struvite uroliths in cats; today, special acidifying low magnesium diets may be used to dissolve sterile struvite stones.
Upper urinary tract stones that involve the renal pelvis and extend into at least 2 calyces are classified as staghorn calculi. Although all types of urinary stones can potentially form staghorn calculi, approximately 75% are composed of a struvite-carbonate-apatite matrix.
Struvite enteroliths 
Wastewater treatment 
Struvite can be a problem in sewage and waste water treatment, particularly after anaerobic digesters release ammonium and phosphate from waste material, as it forms a scale on lines and clogs system pipes. Recovery of phosphorus from wastestreams as struvite and recycling those nutrients into agriculture as fertilizer appears promising, particularly in agricultural manure and municipal waste water treatment plants.
|Wikimedia Commons has media related to: Struvite|
- http://rruff.geo.arizona.edu/doclib/hom/struvite.pdf Handbook of mineralogy
- http://webmineral.com/data/Struvite.shtml Webmineral
- http://www.mindat.org/min-3811.html Mindat
- "Uroliths". Shiloh Shepherd Genetic Task Force. 2008-01. Retrieved 2008-10-26.
- Matsumoto, K.; Funaba, M (2008 Feb volume=1780 issue=2). "Factors affecting struvite (MgNH4PO4·6H2O) crystallization in feline urine". Biochim Biophys Acta.: 233–9. PMID 17976920.
- Blue MG, Wittkopp RW (July 1981). "Clinical and structural features of equine enteroliths". Journal of the American Veterinary Medical Association 179 (1): 79–82. PMID 7251465.
- Robert T. Burns, Lara B. Moody, Forbes R. Walker, D. Raj Raman. "Laboratory and In-Situ Reductions of Soluble Phosphorus in Liquid Swine Waste Slurries". Environmental Technology 22: 1273–1278. Retrieved 2011-07-16.
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- Ostara Nutrient Recovery Technologies. "The Pearl Process". Retrieved 2012-02-25.