What unique reaction do carbonate minerals exhibit when they come in contact with acids?

When carbonate minerals come into contact with acids, they undergo a specific chemical reaction that produces carbon dioxide gas, leading to effervescence, which is the bubbling or fizzing effect that can be observed. This reaction occurs because the acid reacts with the carbonate ions present in the mineral, resulting in the release of CO2. This characteristic fizzing is a distinctive trait of carbonates and is commonly used in laboratory tests to identify these minerals.

The other options do not accurately describe the behavior of carbonate minerals in acid. A change in color does not typically occur as a direct result of acid contact. Hardening further refers to a physical change that does not happen with carbonate minerals in acids, and emitting light is not a property usually associated with carbonate reactions. Therefore, the effervescence exhibited by carbonate minerals when exposed to acids is a clear indicator of their identity and a key characteristic in the study of geology and earth sciences.