They come in two varieties, simply labeled Outcrop and Metallic Outcrop. Regular Outcrops are shown on the Wave Scanner as two lines, far apart. The auditory clue is a "clicking" noise. The Metallic Outcrop is shown on the Wave Scanner as two lines, near the bottom of the scanner and just a bit apart. The auditory clue is a "metallic scraping" noise.
When they are destroyed by weapons fire from a ship or SRV, they explode into chunks of materials, which can be collected using a ship or SRV's Cargo Scoop. Each chunk of a material yields three units of that specific material.