During bonding an atom seeks to fill its outermost energy- level shell. Electrons involved in bonding are called valence electrons. Atoms of the same element with different numbers of neutrons are called isotopes of that element. Each mineral has its own unique crystalline structure. The crystalline structure is electrically neutral.
Polymorphs are different minerals with the same chemical composition.
Different crystalline structures. Different physical properties. Both are composed of Carbon atoms. There are nearly 4000 minerals. The rock-forming minerals are most important to geology.