Apatite
Mohs 5, the mineral phosphate rock is made of, and the mineral bones and teeth are made of — the same compound doing both jobs.
Apatite is a calcium phosphate, and it is the mineral of two apparently unrelated industries: fertiliser and bone. The hard tissue of vertebrates is a poorly crystalline form of it, and so is the rock mined by the hundred million tonnes to feed crops.
Phosphorus has no substitute in agriculture and no atmospheric reservoir to draw on, unlike nitrogen. That makes apatite one of the few minerals whose supply is a genuine constraint on the food system rather than a matter of price.
How to identify it
Apatite is defined as hardness 5 and is best identified by that: it scratches glass poorly or not at all, and is easily scratched by a knife. Its name comes from the Greek for deceit, because it was so often mistaken for other minerals.
Crystals are hexagonal prisms, commonly green or blue-green, sometimes gemmy enough to be cut.
Uses
Almost all mined apatite is treated with sulfuric acid to make phosphoric acid and superphosphate fertiliser. That single use dominates every other by orders of magnitude.
Smaller quantities go into phosphates for detergents, food additives and animal feed. Gem-quality crystals are cut, but the mineral is too soft for jewellery that will be worn hard.
How we know: checked recently · only one source, so there is nothing to cross-check it against · stated directly by the source.
How this connects
Where a connection has been confirmed by an outside reference, that reference is named beside it.
is an ore of
- Phosphorus — element · essentially all phosphorus, and phosphorus has no substitute in agriculture
is a component of
- Carbonatite — rock · abundant enough in some bodies to be mined for phosphate in its own right
- Granite — rock · the phosphate accessory, present in almost every granite and rarely in quantity
- Ivory — material · 65–75% · carbonated hydroxyapatite, around 70 per cent by mass, in a collagen matrix — the same recipe as bone, arranged without the pores
- Bone — material · 60–70% · carbonated hydroxyapatite in crystals a few nanometres thick — small enough to contain no flaw big enough to start a crack, which is most of why bone is tough
is an input to
- Froth flotation — process · the step that makes phosphate rock into fertiliser feed by removing the carbonate and silica around it
- Smelting — process · the phosphate rock charged to the electric furnace, with coke to reduce it and silica to take up the calcium
is a source for
- Lithium iron phosphate — compound · for the phosphate, by way of phosphoric acid — the same rock that makes fertiliser, and there is a great deal of it
contains
- Calcium — element
- Chlorine — element · substitutes within a solid solution — an individual specimen may hold little of it
- Fluorine — element · substitutes within a solid solution — an individual specimen may hold little of it
- Hydrogen — element · substitutes within a solid solution — an individual specimen may hold little of it
- Oxygen — element
- Phosphorus — element
Sources
- Material WorldOur own writing
- Wikimedia Foundation · Creative Commons CC0 1.0 Universal (public domain dedication)