Gyali

Gyali ( "glass", also spelled Giali or Yali, pronounced ) is a volcanic Greek 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). 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 ().
Geography.
The island is long and between and across. It has a cave. Parts of the island undergoing pumice strip mining are barren of vegetation. The 2001 census reported a resident population of 10 people. Administratively, it is part of the municipality of Nisyros. Its also popular for Perli, a thermo powder added in construction.