When two distinct elements are chemically combined—i.e., chemical bonds form between their atoms—the result is called a chemical compound. Most elements on Earth bond with other elements to form chemical compounds, such as sodium (Na) and Chloride (Cl), which combine to form table salt (NaCl).
A specimen can directly be observed under a microscope and is the fastest and best method to check the external composition of the specimen in detail. The success of the identification will also depend on how it's handled treated and stored.