Midwest Hearth Natural Lava Rock Granules for Gas Log Sets and Fireplaces (5-lb Bag)Midwest Hearth Natural Lava Granules will instantly renew and enhance your fireplace. What is lava rock: - Naturally occurring, these lava rocks are formed as volcanic magma rises to the surface, cools and releases gases which gives these rocks their coarse surface. - Because they are volcanic, they can withstand extremely high temperatures without sustaining any damage or crumbling. Features: ? All natural - No added stains or colorants. ? Withstands extremely high temperatures. ? Will not break down or crumble. ? Appropriate size granules for indoor gas appliances. ? Adds realism to your fireplace. ? Hides unsightly burner pans, cracked fire brick, and more. ? Coarse surface works well with optional rock wool and glowing embers. ? Generous bag size is adequate for most fireplace log sets. ? Works with both Natural Gas and Propane appliances.