free download PNG images :Sand

Sand is a natural granular material, which is composed of fine rock and mineral particles. It is defined by size and is finer than gravel and coarser than silt. Sand can also refer to the texture category of the soil or soil type; that is, the percentage of sand in the soil in the mass is more than 85%.

The composition of sand will vary depending on the local rock source and conditions, but in inland and non tropical coastal areas, the most common composition of sand is silica (silica or SiO2), usually in the form of quartz. The second most common type of sand is calcium carbonate, such as aragonite, which has been mainly formed by various forms of life (such as coral and shellfish) in the past 500 million years. For example, it is the dominant form of sand that is apparent in ecosystems where reefs like the Caribbean have dominated for millions of years.

Sand dust is a non renewable resource in human time, and there is a great demand for sand used to make concrete.