Final answer:
Struvite crystals are often described as looking like coffin lids. These kidney stones are composed of magnesium, ammonium, and phosphate, distinct from the more common calcium oxalate stones or calcium phosphate stones which do not take this shape.
Step-by-step explanation:
The type of crystal that is often described as looking like a coffin lid is struvite. Struvite stones, which are not mentioned directly in your provided information, are a type of kidney stone that are composed of magnesium, ammonium, and phosphate. They have a characteristic coffin lid shape when viewed under a microscope, which makes them distinct from other types of renal calculi such as calcium oxalate stones or calcium phosphate stones.
Calcium oxalate stones are the most common type of kidney stone and are associated with factors that promote the precipitation of calcium oxalate crystals in the urine. On the other hand, calcium carbonate crystals can form calcite, which is found in sea urchins' teeth to have special properties allowing them to grind limestone, though these do not generally form the shape resembling a coffin lid.
When considering the formation of kidney stones, it's important to understand that they are largely composed of calcium oxalate and calcium phosphate. Factors contributing to their formation include diet and metabolic conditions that affect the solubility and precipitation of these minerals in the urine.