tufa

• 名词，指一种岩石：既指由矿泉处碳酸钙沉积形成的松软多孔石灰岩（钙华），也指由火山灰压实而成的坚硬火山岩。

A noun referring to a type of rock, either a soft, porous limestone formed from calcium carbonate deposits near mineral springs, or a hard volcanic rock made of compacted volcanic ash.

1. Calcareous tufaC2formal

   A soft, porous sedimentary rock formed by the precipitation of calcium carbonate from mineral-rich spring water.

   钙华

   • The ancient Romans used tufa extensively in their architecture.
   • Tufa formations can be seen around hot springs in the region.
   • The porous nature of tufa makes it lightweight but not very durable.

   同义词calc-tufa

2. Volcanic tuffC2formal

   A hard, compacted rock formed from volcanic ash and other pyroclastic materials.

   凝灰岩

   • The cliffs were composed of volcanic tufa from ancient eruptions.
   • Many buildings in the region are constructed from local tufa stone.
   • Geologists studied the tufa layers to understand the volcano's history.

   同义词tuff