Goethite
Goethite is named after Johann Wolfgang von Goethe, celebrated German poet and scientist.
Goethite may form radiating cluster of deep black crystals or massive stalactites that exhibit a rainbow of iridescent colours.
The material is often cut and polished into interesting free forms.
Goethite may form radiating cluster of deep black crystals or massive stalactites that exhibit a rainbow of iridescent colours.
The material is often cut and polished into interesting free forms.
| General Information | |||||||
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| Chemical Formula |
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| Physical Properties of Goethite | |||||||
| Mohs Hardness | 5 to 5.5, Gemstones (2009) | ||||||
| Specific Gravity | 4.27 to 4.29, Gemstones (2009) | ||||||
| Tenacity | Brittle, Gemstones (2009) | ||||||
| Cleavage Quality | Perfect, Gemstones (2009) | ||||||
| Fracture | Uneven,Splintery, Gemstones (2009) | ||||||
| Optical Properties of Goethite | |||||||
| Refractive Index | 2.26 to 2.398, Gemstones (2009) | ||||||
| Optical Character | Biaxial/-, Gemstones (2009) | ||||||
| Birefringence | 0.138, Gemstones (2009) | ||||||
| Pleochroism | Visible, Gemstones (2009) | ||||||
| Dispersion | Relatively strong, Gemstones (2009) | ||||||
| Colour | |||||||
| Colour (General) | Black, brown, russet, yellow, Gemstones (2009) | ||||||
| Transparency | Opaque, Gemstones (2009) | ||||||
| Lustre | Adamantine,Silky,Dull (Earthy),Metallic, Gemstones (2009) | ||||||
| Crystallography of Goethite | |||||||
| Crystal System | Orthorhombic, Gemstones (2009) | ||||||
| Habit | Botryoidal, stalactitic, bladed, columnar, Gemstones (2009) | ||||||
| Further Information | |||||||
| Mineral information: | Goethite information at mindat.org | ||||||
| Significant Gem Localities | |||||||
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