Inorganic limestone (primarily calcium carbonate) and inorganic gypsum (hydrated calcium sulfate) are chemically distinct minerals with different atomic formations, making this a matter of common chemical knowledge.
The claim states that inorganic limestone and inorganic gypsum have distinct chemical formations. Limestone is composed primarily of calcium carbonate (CaCO3), whereas gypsum is calcium sulfate dihydrate (CaSO4·2H2O). Because these are fundamentally different chemical compounds with distinct and well-established definitions in basic chemistry and mineralogy, this is a matter of common knowledge and requires no citation.