goethite
goethite crystals from France
inclusions of lepidocrocite and goethite in a Brazilian quartz oval cut
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
APPROACHING GEMS
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
voillot-joaillier.fr
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