- Petroleum has revolutionized civilization since its industrial production began.Photo (c) Andrew Alden, licensed to About.com (fair use policy)
- Blob of raw crude oil at Coal Oil Point, Santa Barbara, California. Large version in Mineral Galley.Permission of Matt Cohen
- Natural asphalt from the McKittrick tar seep, California. Large version in Rock Gallery.Photo (c) Andrew Alden, licensed to About.com (fair use policy)