Gold Sheen Obsidian Tumble

Obsidian is a naturally occurring volcanic glass formed in swiftly cooling lava that has a high silica content. It is not considered a true mineral, as it does not have an entirely consistent chemical content (it is considered to be completely amorphic) and it does not form crystals (no crystal structure)
Golden sheen obsidian is formed when patterns of gas bubbles are aligned along layers created by the flowing lava before it solidified.