THE MINERAL LIMONITE

  • Chemistry: A mixture of hydrated iron oxides
  • Class: Oxides and Hydroxides
  • Uses: Important ore of iron, as a pigment and as mineral specimens.
  • Specimens
Limonite is not a true mineral but a mixture of similar hydrated iron oxide minerals. Most of limonite is made up of Goethite. Massive Goethite and Limonite can be indistinguishable. Limonite forms mostly in or near oxidized iron and other metal ore deposits, and as sedimentary beds. Limonite has been known to pseudomorph other minerals such as pyrite, meaning it replaces a crystal of pyrite with limonite but keeps the shape of the pyrite crystal.

PHYSICAL CHARACTERISTICS:

  • Color is yellow, orange, reddish brown, brownish black.
  • Luster is earthy to dull.
  • Transparency is opaque.
  • Crystal System is undefined.
  • Crystal Habits include massive, layered, botryoidal and stalactitic.
  • Cleavage is absent.
  • Fracture is crumbly or earthy.
  • Hardness is variable 4 - 5.5
  • Specific Gravity is variable at 2.9 to 4.3 (average to above average)
  • Streak is brownish yellow to yellow.
  • Associated Minerals include a large list of minerals particularly secondary deposit minerals.
  • Notable Occurrences include many iron mines around the world, especially nice specimens come from Europe, Mexico, Canada and northeastern USA.
  • Best Field Indicators are lack of crystal forms, lack of cleavage and streak.
LIMONITE specimens:
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LIMONITE specimen lim-1
$ 30.00
Dims: 3.2 x 1.6 x 1.5" (8.1 x 4.2 x 3.9 cm)
Wt: 4.1 oz. (117 g)
Washington County, Missouri, U.S.A.
A few dozen dull, dark brown Limonite crystals coat the siliceous base of this hand specimen. They are in very good condition, showing little damage, and reach lenghts of nearly 0.4" (1 cm). As the crystals pseudomorphed from marcasite, they have retained the orthorhombic form and "coxcomb" habit of that mineral- most of the "coxcombs" are quite well-defined. The Limonites appear to rest on a thin crust of slightly drusy agate.
no photo
lim-1 ($ 30.00)
Washington County, Missouri, U.S.A.
LIMONITE specimen lim-2
$ 25.00
Dims: 1.0 x 1.0 x 0.8" (2.5 x 2.4 x 2.0 cm)
Wt: 0.5 oz. (15 g)
Boulogne, France
This large thumbnail piece consists of a cluster of Limonite crystals that were pseudomorphed from marcasite. They are in excellent condition and reach lengths of up to 0.5" (1.2 cm). All have retained the excellent orthorhombic bladed form of the marcasite, but have a dull, rust-brown coloration and a dull waxy to matte luster. Also, the cluster is less dense than it would be were the crystals still composed of marcasite. There is no host rock present, and the piece is affixed inside a plastic thumbnail box.
no photo
lim-2 ($ 25.00)
Boulogne, France
LIMONITE specimen lim-3
$ 25.00
Dims: 2.65x1.79x1.46" (6.74x4.55x3.71cm)
Wt: 4.06oz (114.8g)
Pomarolli Mine, Divino das Laranjeiras, Minas erais, Brazil
This limonite "crystal" is a pseudomorph after siderite, and is accompanied by a large number of mica books, probably biotite. The limonite is opaque and a mottled brown in color, with a surprizingly good luster. The mica is brown and transparent in very thin sections (showing brown highlights).
no photo
lim-3 ($ 25.00)
Pomarolli Mine, Divino das Laranjeiras, Minas erais, Brazil
 

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