In nature, only a few elements occur in their native form as a single, solid element, not chemically combined with others. Gold, the best known example, is less chemically active than most other elements that exist in solid form. Gold occurs as tiny particles in rocks; as hot water seeps through bedrock, it may carry the gold bits until they accumulate into small nuggets. A few other metals, such as silver and copper, are sometimes found in small standalone amounts in nature. Whether silver, copper, and platinum combine with other elements or remain as native elements depends on their proximity to other chemically active substances. A few nonmetallic elements also may occur in native form. For example, plain sulfur collects around the vents of hot springs and volcanoes, as well as in sedimentary structures like salt domes. In nature, carbon can appear in two different native forms, graphite and diamond, depending on how much heat and pressure have been applied to it.