Detailed sheet

goethite

It is known and used since prehistory, prehistoric people used it as a pigment for paint in the caves, such as at Lascaux. It was identified in 1806 by the mineralogist Johann Georg Lenz (1748-1832) and its name honors the German writer Goethe. This is a very common inclusion in many minerals, as needles or flakes. The lepidocrocite which is red-orange is the dimorph of goethite, it constitutes colored inclusions sometimes associated with black goethite in quartz and it is one of the constituents of the limonite. Lepidocrocite is sometimes called pyrrhosiderite.



CHEMICAL CHARACTERISTICS

FeO(OH)

iron hydroxide



PHYSICAL CHARACTERISTICS

Main color

brown

Other colors

black

Color of streak

brown, yellow

Luster

metallic

Hardness

5.0 to 5.5

Density

3.80 to 4.30

Cleavage

perfect

Fracture

fibrous, uneven



OPTICAL PROPERTIES

Transparency

opaque, translucent

Refractive index

2.270 - 2.420

Double refraction

0.133

strong biaxial (-)

visible double refraction

No

Dispersion

0,140

Pleochroism

weak

Number of colors

3

yellow, brown, orange

Fluorescence

none



CRYSTALS PROPERTIES

botryoidal masses, tufts of acicular crystals, elongated prismatic ...

crystals system

orthorhombic



OTHER INFORMATIONS

Exploited
sites

It is found in France in the Indre in the Chaillac Mine and in the Mont Roc mine in the Tarn. It is found in the whole world, on the five continents where there are numerous deposits: U.S., Canada (Ontario), South America, Australia, China, Russia, Africa, England, Cornwall and throughout continental Europe ….

use in jewelry

it is cut in facets or cabochon

Historical
healing properties

Such as hematite, it would have been used to compensate iron deficiencies, and is associated with blood. Hematite it is often preferred to it having the same properties but stronger.

Other
Gems

Venez visitez

notre site web

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