Gyali

Gyali (Greek: Γυαλί "glass", also spelled Giali or Yali, pronounced [ʝaˈli]) is a Greek volcanic island in the Dodecanese, located halfway between the south coast of Kos (Kardamaina) and Nisyros. It consists of rhyolitic obsidian lava domes and pumice deposits (which are mined in huge quantities). No historical eruptions are known, but the most recent pumice eruptions overlie soils containing pottery and obsidian artifacts from the Neolithic period (10,000–4,500 BC). The island has two distinct segments, with the northeastern part almost entirely made of obsidian and the southwestern part of pumice. These are connected by a narrow isthmus and beach made of modern reef sediments. Anciently, the island was known as Istros (Ancient Greek: Ἴστρος).