Granite or quartzite stone chips - 9.5mm road stone
Granite is a hard, coarse grained rock that makes up a large part of every continent. It is classified as an igneous rock formed by the slow cooling and crystallisation of molten magma. Granite consists mainly of three minerals - quartz, alkali feldspar, and plagioclase feldspar, which give the granite its distinctive white, pink or light grey colouring.
Quartzite is also a hard coarse grained rock found all over the world. It is classified as a metamorphic rock formed when quartz sandstone is subjected to heat and pressure during mountain building events at convergent plate boundaries. Quartzite consists mainly of quartz and also comes in a range of white, pink or grey colours.
The two rock types are very similar in appearance and quartzite is often mistaken for a light coloured granite.
The interlocking crystalline nature of these rocks make them strong and durable and capable of withstanding weathering for hundreds of years. This fact, along with their common occurrence on all continents, has made them the most commonly used materials in both the construction and road building industries. They are also a highly suitable inert medium for hydroponics.
The stone medium required by the gravel flow systems is a widely available product crushed and screened by most quarries for use in road building and concrete construction operations. It is crushed and screened to limit the chip size to 9.5mm. In South Africa the stone is most often described as "nine and a half (9 1/2) road stone". Often the quarry will wash or double wash this product before delivery to remove the dust and fine particles. This wash, while it is helpful, is not sufficient for the purposes of the hydroponics system, and the stone requires further washing to remove all dust and fine particles. The stone medium will last a lifetime and will not need to be replaced.
For commercial system users most quarries will quote a (delivered) per ton or cubic metre price. Contact a quarry near you to confirm availability and current pricing.
For our tray systems we supply the correct stone washed and ready to use, and packed in 22kg bags.
Each tray requires 8 bags.
Single tray system (8 bags)
Double tray system (16 bags)