Native elements are minerals composed of only one element, such as copper, sulfur, gold, silver, and diamonds. These native elements are not common in Kentucky, but are mentioned because of their collector appeal.
Crystal system: isometric. Cleavage: perfect octahedral. Color: colorless, pale shades of yellow, orange, or blue. Hardness: 10. Specific gravity: 3.5. Uses: jewelry, saws, polishing equipment.
Diamonds, the hardest of any naturally formed mineral, are also highly refractive, which causes light to be split into a spectrum of colors commonly called play of colors. Because of its high specific gravity, it is easily concentrated in alluvial gravels, where it can be mined. This is one of the main mining methods used in South Africa, where most of the world's diamonds originate. The source rock of diamonds is the igneous rock kimberlite, also referred to as diamond pipe. A non-gem variety of diamond is called bort.
Kentucky has kimberlites in Elliott County in eastern Kentucky and Crittenden and Livingston Counties in western Kentucky, but no diamonds have ever been discovered or authenticated in these rocks. A diamond was found in Adair County, but it was determined to have been brought in from somewhere else.
Crystal system: orthorhombic. Fracture: uneven. Color: yellow. Hardness 1-2. Specific gravity: 2. Sulfur smell, burns easily.
Sulfur crystals occur in geodes and nodules in the Borden-Ft. Payne Formation in south-central Kentucky.
Crystal system: isometric. Cleavage: octahedral. Color: brilliant yellow, paler if it has high silver content. Hardness: 2.5-3. Luster: metallic. Specific gravity: 19.3. Tenacity: malleable and ductile. Uses: jewelry, coins.
Gold is not common in Kentucky, but is included here because of its appeal. Gold has been of value to mankind for centuries because of its color, weight, and malleability.
Gold commonly occurs in microscopic amounts in the earth and in seawater, and it commonly is found in quartz veins associated with igneous and metamorphic rocks.
Silver (color: gray to silver white; hardness: 2.5-3; specific gravity: 10.5) and platinum (color: steel gray; hardness: 4; specific gravity: 21.5) do not have good cleavage and are not common in Kentucky, but are sometimes associated with gold.