The lithology consists mostly on carbonate concretion layers, mixed with abundant pyrite and euhedral crystals. After calcification, the conjunctival cyst hardens and forms a conjunctival concretion. It is a naturally occurring, non-nacreous, calcareous concretion (pearl) from a giant clam. Each fossil was a leaf preserved in an individual ironstone concretion. The type specimen was found in an iron-cemented sandstone concretion near Salina. The answer is that the concretion itself is not Ordovician. An enterolith is a mineral concretion or calculus formed anywhere in the gastrointestinal system. Congenital conjunctival concretion condition is also more common. The specimen was encased in a single concretion. The crystallinity is higher in the centre of a concretion. Parts of the specimen were also cracked due to being part of a septarian concretion. It took conservators over a year to remove all the concretion from the outer hull.