When are atoms considered stable? when they have satisfied the law of conservation of mass naturally or through bonding to obtain
full valence shells

when they have satisfied the octet rule naturally or through bonding to obtain full valence shells

when their valence electrons have "fallen" back to ground state through bonding

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).