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See also: hydrate named from the Gr. ketgiav (meadow), in allusion to its occurrence as " bog-ore " in meadows and marshes
.
It is never crystallized, but may have a fibrous or microcrystalline structure, and commonly occurs in concretionary forms or in compact and earthy masses; sometimes mammillated, botryoidal, reniform or stalactitic
.
The colour presents various shades of See also: brown and yellow, and the streak is always brownish, a character which distinguishes it from
See also: haematite with a red, or from See also: magnetite with a black streak
.
It is sometimes called brown haematite
.
See also: Limonite is a ferric hydrate, conforming typically with the See also: formula Fe403(OH)6, or 2Fe2O3.3H2O
.
Its hardness is rather above 5, and its specific gravity varies from 3.5 to 4
.
In many cases it has been formed from other iron oxides, like haematite and magnetite, or by the alteration of See also: pyrites or See also: chalybite
.
By the operation of -meteoric agencies, iron pyrites readily pass into limonite often with retention of See also: external See also: form; and the masses of " gozzan " or gossan " on the outcrop of certain See also: mineral-See also: veins consist of rusty iron ore formed in this way, and associated with cellular See also: quartz
.
Many deposits of limonite have been found, on he:ng worked, to pass downwards into ferrous carbonate; and crystals of chalybite converted superficially into limonite are well known
.
Minerals, like See also: glauconite, which contain ferrous silicate, may in like manner yield limonite, on weathering
.
The ferric hydrate is also readily deposited from ferruginous See also: waters, often by means of organic agencies
.
Deposits of brown iron ore of greateconomic value occur in many sedimentary rocks, such as the
.
See also: Lias, Oolites and See also: Lower See also: Greensand of various parts of See also: England
.
They appear in some cases to be altered limestones and in others altered glauconitic sandstones
.
An oolitic structure is sometimes See also: present, and the ores are generally phosphatic, and may contain perhaps 30% of iron
.
The oolitic brown ores of See also: Lorraine and Luxemburg are known as " minette," a diminutive of the French mine (ore), in allusion to their low content of See also: metal
.
Granular and concretionary limonite accumulates by organic See also: action on the floor of certain lakes in Sweden, forming the curious " lake ore." Larger concretions formed under other conditions are known as " bean ore." Limonite often forms a cementing See also: medium in ferruginous sands and gravels, forming " See also: pan "; and in like manner it is the agglutinating See also: agent in many conglomerates, like the See also: South See also: African " See also: banket," where it is auriferous
.
In iron-shot sands the limonite may form hollow concretions, known in some cases as " boxes." The " eagle stones " of older writers were generally concretions of this kind, containing some substance, like See also: sand, which rattled when the hollow nodule was shaken
.
Bog iron ore is an impure Iimonite, usually formed by the influence of micro-organisms, and containing See also: silica, phosphoric acid and organic See also: matter, sometimes with manganese
.
The various kinds of brown and yellow ochre are mixtures of limonite with See also: clay and other impurities; whilst in See also: umber much manganese See also: oxide is present
.
Argillaceous brown iron ore is often known in Gel-dimly as Thoneisenstein; but the corresponding See also: term in See also: English (clay iron See also: stone) is applied to nodular forms of impure chalybite
.
J
.
C
.
See also: Ullmann's name of stilpnosiderite, from the See also: Greek yr X,ryos (shining) is sometimes applied to such kinds of limonite as have a pitchy lustre
.
Deposits of limonite in cavities may have a rounded See also: surface or even a stalactitic form, and may present a brilliant lustre, of blackish colour, forming what is called in See also: Germany Glaskopf (See also: glass See also: head)
.
It often happens that analyses of brown iron ores reveal a larger proportion of See also: water than required by the typical formula of limonite, and hence new See also: species have been recognized
.
Thus the yellowish brown ore called by E
.
See also: Schmidt xanthosiderite, from YawBos (yellow) and old,tpos (iron), contains Fe20(OH)4, or Fe2O3.2H20; whilst the bog ore known as limnite, from Xt w,t (See also: marsh) has the formula Fe(OH)3, or Fe2O3.3H2O
.
On the other See also: hand there are certain forms of ferric hydrate containing less water than limonite and approaching to haematite in their red colour and streak: such is the mineral which was called hydrohaematite- by A
.
Breithaupt, and is now generally known under R
.
Hermann's name of turgite, from the mines of Turginsk, near Bogoslovsk in the Ural Mountains
.
This has the formula Fe40i(OH)2, or 2Fe203•HzO
.
It probably represents the partial dehydration of limonite, and by further loss of water may pass into haematite or red iron ore
.
When limonite is dehydrated and deoxidized in the presence of carbonic acid, it may give rise to chalybite
.
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BROWN ORE- According to appearance of iron ore, the limonite iron ore is also known as BROWN ORE. In limonite Fe content is about 60% & rest 40% , maximum is moisture & minor amount of other impurities content.
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