Perlite
Perlite is sodium potassium aluminosilicate, it is a naturally occurring mineral, and therefore non-renewable. It a dark grey type of volcanic glass which formed when volcanic obsidian glass is saturated in water over a long period.
In its natural raw state it has a density of around 1100 kg/m3 and solid, it is generally more commonly known in its expanded or processed state. When heated to temperatures of up to 980-C it softens and the entrapped water is released as steam which causes particles in their plastic state to expand up to 20 times their original size.
The expanded form of perlite has a density of between 30–150 kg/m3, a neutral pH level, efficient at absorbing small amounts of water, and draining water as it is spherical and with some insulating qualities due to its inherent air gaps.
It has been used in agriculture for many centuries, partly because the volcanic areas where it is found are also fertile soils. Today it is used in common gardening, hydroponics and in construction as a lightweight aggregate in concrete, as filling material, acoustic or insulation application and in fireproofing.
The global reserves of perlite are estimated to be around 700 million tonnes, with around 500,00 tonnes produced each year primarily from Greece, the US, Turkey, and Japan. Vermiculite is a very similar material to perlite with similar uses but some slightly different characteristics.
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