It could be said that the use of natural abrasives dates back to the early years of the human species. Without them, man would probably not have been able to sharpen and shape his first weapons or the rustic tools of antiquity. Today, however, natural abrasives have been losing their importance due to the rise of synthetic abrasives, which have more optimally met the demands of the various industries in which they are used.
Do you want to know what natural abrasives are and which are the most common ones? In this article we tell you.
What are natural abrasives?
Natural abrasives are minerals or rocks of high hardness that are born in the earth’s crust and are extracted and processed to make abrasive tools that serve to shape other materials of lesser hardness by grinding or abrasion.
They are very common in nature and are generally used in a wide variety of industrial, domestic and technological tasks.
Gradually, however, most natural abrasives have been replaced by synthetic materials, because the fields of application of abrasives require materials with more consistency and greater resistance to wear. With the exception of natural diamond, which has a hardness of 10 on the Mohs scale, almost all abrasives born in the earth’s crust are highly variable in their properties and hardness.
Normally, it is not recommended to use natural abrasives in the rough, because if they are not processed, it is not possible to obtain quality finishes, due to the impurities they possess in their natural state.
The most common natural abrasives
Emery is a very hard rock that is used to make abrasive dust. According to experts, it is considered the historical abrasive par excellence.
It is composed of corundum (aluminium oxide) mixed with some traces of spinels containing iron, hercynite, magnetite and rutile (titania) and is black or dark grey in colour, less dense than transparent corundum, with a specific gravity of between 3.5 and 3.8.
Emery is used as an abrasive in grinding stones (grinders) and in tools for cutting and polishing metals, some very fine grains can also be used for highly technical polishing, such as the preparation of metallurgical samples requiring very close tolerances.
Also called Almandita, it belongs to the group of neosilicates and is classified as natural silicate mineral.
There are very hard varieties that are used as abrasives due to this characteristic and they are still used in some sandpapers for the wood industry. They are also used for sandblasting and waterjet cutting; glass polishing and buffing, coated abrasives, organic bonded abrasives, etc.
Although the different species of garnet have very similar physical properties and crystalline forms, they have different chemical components, but in their natural form they come in many colours, such as red, purple, pink, green, blue, orange, yellow, brown, black and colourless.
Quartz is found in large quantities all over the Earth’s crust. As an abrasive it is used under the name of silica sand. It is also the most widely used abrasive due to its low price. It is used in the manufacture of sandpapers, discs or blocks, and mainly in systems of abrasion by means of a sandblast under pressure.
As with other natural abrasives, the use of quartz has decreased, but it is still used in low-priced abrasive products, for the manufacture of grinding wheels, centreless grinding wheels and slow grinding machines.
This natural abrasive is of volcanic origin and is composed of volcanic glass pyroclastic with a rough and highly vesicular texture that may or may not contain crystals, with very thin and translucent bubble walls of extrusive igneous rock.
It is usually light in colour. It is used as an abrasive material in setting work, in block form for grinding or cleaning, or is ground into powder for polishing and cleaning applications.
Diamond is a crystalline state of carbon and is the hardest natural material yet known. As an abrasive, its structure is very resistant to wear and tear and abrasion. For example, its resistance is 140 times greater than that of corundum despite the fact that both are ranked 9 and 10 on the Mohs scale.
It is used for cleaning and grinding of grinding wheels or on interchangeable blades for fine turning of non-ferrous metals.