Answer:
Rock gypsum and rock salt can be distinguished based on their physical properties. Here are a few ways to differentiate between the two:
1. Appearance: Rock gypsum is typically white or colorless and has a pearly or glassy luster. It often forms in large, crystalline masses or fibrous layers. On the other hand, rock salt is usually transparent or translucent and appears as colorless or various shades of pink, red, or brown. It commonly occurs as cubic or rectangular crystals.
2. Taste: One of the simplest ways to differentiate rock gypsum from rock salt is by taste. Rock salt has a distinct salty taste due to its high sodium chloride content, while rock gypsum is not salty and has no taste.
3. Solubility: Rock salt is highly soluble in water, meaning it easily dissolves when in contact with water. In contrast, rock gypsum is relatively insoluble and does not dissolve readily in water.
4. Hardness: Rock gypsum has a Mohs hardness of 2, which means it is relatively soft and can be easily scratched with a fingernail.