Struvite crystals. St. Nikolai Church, Hamburg, Germany.
These are ammonia phosphate crystals. They are generally found in the urine of animals with kidney problems. Despite their biological origin, struvite crystals were first described on the site of St Nikolai Church, Hamburg. They were initially attributed to the presence of a medieval midden on the site.
Struvite is an organic mineral. it may also be an anthropocene mineral -- a mineral which forms in the earth due to the influence of humans on their environment. In this case the large scale storage of waste by-products either by humans or by animals which they have kept in one place.
Prices are per item. In this case per vial. The photograph is representative of the item offered for sale, but you may get either of the vials in this picture.