Crystals in Canned Seafood

Canned seafood products sometimes contain small crystals that look like glass. These crystals are quite large to be noticeable; and some consumers may even think that there is a foreign substance in their food. In fact, these fragments are harmless. These small crystals turn out to be fragments of a substance known as magnesium ammonium phosphate.

Magnesium ammonium phosphate is an inorganic compound, a complex salt of ammonium, magnesium metal and phosphoric acid with the formula NH4MgPO4, colorless crystals insoluble in water form crystalline hydrates.

Also known as “struvite“ – – (NH4) MgPO4 * 6H2O

Molecular weight 245.41
Name origin Was named after the German mineralogist and diplomat in the Russian service, Heinrich Antonovich Struve (Heinrich Christoph Gottfried von Struve, 1772-1851), who published  “Works on mineralogy, mainly regarding Württemberg and the Black Forest” and “Mineralogy and Geology of North America”, Honorary Member of the St. Petersburg Academy of Sciences.
IMA status Valid, described for the first time until 1959 (before IMA)
Opening year 1846

Struvite is located in the deposits of guano, in peatlands rich in organic matter. Struvite as a biogenic mineral is often found in the decomposition products of organic compounds in a putrefactive environment, resulting from the action of bacteria on organic compounds, also known as an integral part of kidney stones and stones in the bladder and in the alkaline urine of infected people.

Physical properties

Mineral color colorless, white (dehydrated), yellow or brownish, light gray; colorless in internal reflexes and brightly.
Trait color white
Transparency transparent, translucent
Shine glass
Cleavage clear in {001}, perfect; according to {100}, very imperfect
Hardness (Mohs scale) 1.5 – 2
Kink uneven, close to cancerous
Strength fragile
Density (measured) 1.711 g/cm3
Density (estimated) 1.705 g/cm3
Radioactivity (GRapi) 0
Electrical properties of the mineral Pyroelectric. Piezoelectric.

Optical properties

Type biaxial (+)
Refractive indices nα = 1.495 nβ = 1.496 nγ = 1.504
2V angle measured: 37° , calculated: 40°
Maximum birefringence δ = 0.009
Optical relief moderate
Optical axis dispersion relatively weak

Crystallographic properties

Point group mm2 – Pyramidal
Syngonia Rhombic (orthorhombic)
Cell options a = 6.94Å, b = 11.2Å, c = 6.13Å
Attitude a:b:c = 0.62 : 1 : 0.547
Unit cell volume V 476.47 ų (calculated by unit cell parameters)
Twin The acute poles of [001] unite in the composition plane {001}, with deep re-entrant angles.

Not soluble in water.

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