When it comes to beautiful islands, Greece has a lot of them. A lot. The popular islands like Santorini and Mykonos are certainly worth it. But a few words about Milos, it might be enough for you to add it to your list.
Obsidian is a rock originating from volcanic regions of young geological age. It is produced when felsic lava extruded from a volcano cools rapidly with minimal crystal growth and it is commonly found within the margins of rhyolitic lava flows known as obsidian flows.