泉質

1. Origins, structure, and basic meaning

• Structure: 泉質 (せんしつ) denotes the chemical or physical properties of hot-spring water. Both examples use 泉質が, once in description and once in comparison.
• Basic usage: An inn guide records the water properties in detail; even within one region they differ by source.

2. Common pitfalls and similar expressions

• Properties documented and properties varying by source
  • The first predicate is 書かれていた; the second is 異なる. The word concerns the water itself, not a hot spring's atmosphere or facilities.