Actinobacteria sp. are organisms called chemoorganohetereotrophs. They do not use oxygen to breathe. They break down organic material and convert it to inorganic material. Which part of the carbon cycle does this describe?

photosynthesis
respiration
decomposition
assimilation

answer is: naturally occurring solid, inorganic compound or element is mineral.

minerals usually have crystalline form, that means than crystal constituents (atoms, molecules or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions.

for example magnetite is a mineral of iron oxide (fe₂o₃).

calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (caco₃).

dolomite is an   carbonate mineral composed of calcium magnesium carbonate (camg(co₃)₂).