rocks-and-gems-obsidian This rock starts out as superhot magma. Then as lava. When lava cools super quickly as it hits air or water, it turns into shiny, sharp rock – obsidian. In ancient times, it was used as a mirror or made into arrowheads.… ← Previous Image Next Image → ↑ Return to post Leave a Reply Cancel reply Your email address will not be published. Required fields are marked *Comment Name * Email * Website This site uses Akismet to reduce spam. Learn how your comment data is processed.