Obsidian Turtle

Obsidian is a natural volcanic glass formed after eruptions and comes in a few different forms, including Snowflake Obsidian, Rainbow Obsidian, and Sheen Obsidian. The use of Obsidian dates back to the Stone Age, and it has been used for thousands of years since in weaponry and rituals. The Mesoamericans and the Mayans polished it into mirrors for use in contacting spirits and as portals to other realms. One such Aztec scrying mirror that belonged to Elizabethan astrologer and mathematician Dr. Dee is on display in the British Museum. 
Black obsidian has found fame in recent years as the Dragon glass in the popular TV series Game of Thrones, where it is forged into weapons to kill the White Walkers. Some ancient people believed that black obsidian were fragments of Satan's claw. Mexicans called it the God of Stones, as they used it so much in everyday life, including forging weapons from it. It has such a sharp edge that even today, precision surgical scalpels are made from obsidian.