These 1 to 2-inch sized lava stones are formed when volcanic lava comes into contact with cool water from the ocean and hardens as a result. The naturally occuring lava stones are gathered up and then go through a 'tumbling' process which removes any sharp edges and gives them their uniform shape. Because they are volcanic, they can withstand extreme temperatures without crumbling or exploding. Tumbled lava stones give a truly unique and stylish look to any gas fireplace which is a refreshing change from the usual fire wood. They may be used exclusively, or as a base for other fireplace ornaments, such as fire glass or lite stones. The best part is they require no maintenance at all! Includes 20 pounds of 1 to 2-inch sized tumbled lava stone.