Segnitite
A variety of Dussertite Group
What is Segnitite?
Segnitite is a rare mineral that occurs in transparent and translucent green and yellow shades of brown. Segnitite is found in oxidation zones around hydrothermal conditions, especially where there are large concentrations of lead and zinc. This mineral is named after Australian gemologist and geologist, Edgar Ralph Segnit. It is sometimes confused with beudantite.
Uses & Applications
Segnitite itself has no practical uses. However, it is an indicator mineral, often found among ore minerals such as pyrite, galena, sphalerite, and more, that have an important role industrial production processes. Its translucent form can be a curious collection specimen.
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Key Characteristics
Characteristics of Segnitite
Segnitite exhibits weak pleochroism from a pale yellow to a more moderate yellow under different angles of plane polarized light, although the effects can be much more dramatic under polarized light. Dichroism and trichroism are both types of pleochroism. The term dichroism is used to describe optical properties of minerals that are uniaxial, including segnitite. Minerals that exhibit dichroism are generally trigonal, hexagonal and tetragonal. A response from UV light was not observed from segnitite.
Formation of Segnitite
Segnitite was first discovered in Broken Hill ore deposit in Broken Hill, New South Wales, Australia. It was first found in the oxidized zone of lead and zinc sulfide ores bodies of the Broken Hill ore deposit and forms in similar settings around the world. Segnitite is a relatively uncommon mineral, and it not found in very large quantities, but is found worldwide in similar areas. Segnitite has since been found in many localities in Western Europe, specifically in sites near Switzerland, Germany and Austria. Segnitite is commonly found alongside many well known minerals including anglesite, galena, jamesonite, linarite, arsenopyrite, cerussite, covellite, cuprite, sphalerite, sulfur, beudantite, cassiterite, pyrite, smithsonite, carminite and plumbojarosite. Many of these minerals are important ore minerals. Segnitite poses some importance when considering the overall composition of surrounding rock.
Composition of Segnitite
The mineral segnitite is a part of the alunite-jarosite family which is a part of the alunite supergroup, which has a general formula of AB3(TO4)2(OH)6. Minerals in the alunite-jarosite family have the general formula AB3(XO4)2(OH)6. More specifically, Segnitite is a part of the low-S lusungite group of alunite-jarosite minerals. The lusungite group falls on the lower third of the ternary diagram, with the jarosite group on top, having the highest content of sulfur. The beudantite-corkite group lies in the middle third on the ternary diagram, possessing intermediate amounts of sulfur. The lusungite group then has the lowest amount of sulfur, and has end members segnitite and lusungite, which then have varying amounts of arsenic to phosphorus; segnitite is the arsenic rich end member of the lusugnite group. Through electron microprobe analysis on the basis of 14 oxygen atoms, the empirical formula of segnitite was found to be (Pb1.05-Ba0.03)1.08(Fe2.76Zn0.22Al0.17Cu0.01)3.16[(AsO4)1.85 (PO4)0.05-(SO4)0.04]1.94(OH,H2O)6.24. Four alternative and simplified versions include: (1) PbFe3(AsO4)2(OH)5*H2O, (2) PbFe3(AsO4)2(OH,H2O)6, (3) PbFe3(AsO4)(AsO3OH)-(OH)5, (4) PbFe3H(AsO4)2(OH)6, although the preferred formula is PbFe3H(AsO4)2(OH)6, which is most consistent with the space group (R3m) for Segnitite.
Health & Safety Information
- ⚠️Harm Reason: Segnitite dust is toxic because it contains heavy metals Arsenic, Lead.
- ⚠️How to prevent the risks of Segnitite?
Quick Facts
Physical Properties
- Color
- Greenish to yellowish-brown
- Hardness (Mohs)
- 4
- Density
- 4.77 g/cm³
- Streak
- Pale yellow
- Luster
- Vitreous, Adamantine
- Crystal System
- Trigonal
Chemical Properties
- Chemical Formula
- PbFe3+3AsO4(AsO3OH)(OH)6
- Elements
- As, Fe, H, O, Pb
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