Iron

What are iron ores? There are four common ores of iron which are found in Tennessee:

  • Magnetite: Iron Oxide (Fe3O4) Oxide Group; hardness 5.5-6.5; specific gravity 4.9-5.2
  • Hematite: Iron oxide (Fe2O3) Oxide Group; hardness 5.5-6.5; specific gravity 4.9-5.2 hardness 5-6; specific gravity 4.9-5.3
  • Limonite: Hydrous iron oxide (FeO(OH)* n(H2); Oxide Group; hardness 5.5-6.5; specific gravity 4.9-5.2 hardness 4-5.5; specific gravity 2.7-4.3
  • Pyrite: Iron Sulfide (FeS2) Sulfide Group; Hardness 6-6.5, specific gravity 4.9-5.2
Where is it found?

When was it deposited?
Quaternary
Tertiary
Cretaceous
Jurassic
Triassic
Permian
Pennsylvanian
Mississippian
Devonian
Silurian
Ordovician
Cambrian
Proterozoic

How iron is used? The uses of iron are too well known to need repeating. Iron is used for implements, appliances, etc.

How is iron mined and processed? Iron was generally mined from small pit mines. This is because the deposits were small and scattered.

Iron is extracted from iron oxide by a process know as smelting. In this process, iron oxide is heated in the presence of carbon monoxide (CO). The oxygen in the iron oxide attaches to the CO to form carbon dioxide (CO2), leaving iron.

On the right is a picture of a 19th century iron furnace make of limestone blocks in Humphreys County

from Tennessee Minerals Annual, TN Division of Geology Bulletin 83, 1992.
History of Iron ore mining in Tennessee: Pyrite is never mined for iron (Although it is sometimes mined for sulfur). Of the three oxides, only two, hematite and limonite, have been commercially mined in Tennessee. Iron mining, both in east and west Tennessee from the late 18th century through the 1930's.


Blast furnace at Wrigley, TN (Hickman Co) from TN Division of Geology Bulletin # 39
The Brown Iron Ores of the Western Highland Rim, TN, by Ernest F Burchard 1934
Environmental impact of iron mining: It was not so much the mining of iron, but the smelting that has harmed the environment. Early 19th century iron manufacturers on the Western Highland Rim used wood to make charcoal for the smelting process. They largely deforested the area before railroads were built bringing coal from east Tennessee to use in the process.