A mineral is a natural, elementary substance or compound formed by geologic processes. Minerals are the components of rocks and mineral ores. Approximately 4,145 minerals are currently known; most are inorganic solid substances, whereas there are only a dozen liquid, gaseous or organic minerals. An elementary substance or chemical compound that comes from outside the Earth is called a cosmic mineral, and a simple substance or compound similar to a natural mineral obtained by artificial means is called a synthetic mineral. Minerals are important material resources that are widely used in the agricultural, industrial and science and technology sectors. Many minerals have special crystal forms or compositions and unique physical properties, such as colour, lustre and pattern, allowing them to become ornamental stones and natural landforms that are unique tourism resources.