Of the several properties used for identifying minerals, it is good to consider which will be most useful for identifying them in small grains surrounded by other minerals.
This type of challenge of identifying minerals in such a messy environment full of other surrounding minerals seems pretty challenging. However it seems there are tests to ease this challenge and there consideration in finding the best method for it.
The most common mineral precipitated by organisms is calcite, or calcium carbonate (CaCO3). Calcite is often precipitated by organisms as a polymorph called aragonite. Polymorphs are crystals with the same chemical formula but different crystal structures. Marine invertebrates such as corals and clams precipitate aragonite or calcite for their shells and structures. Upon death, their hard parts accumulate on the ocean floor as sediments and eventually may become the sedimentary rock limestone.
This example of corals and clams turning calcite or agaronite that has precipitated, into a form of protection, then becoming the sedimentary rock limestone upon death shows how living organisms use these elements and eventually become apart of a geological formation.
Typically, substances like coal, pearl, opal, or obsidian that do not fit the definition of a mineral are called mineraloids.
I assumed some of these were minerals before reading but I see they are classified as mineraloids since they don't have the feature of crystalline and aren't made from geologic process.