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News: Researchers identified two hydrous sulphate minerals, melanterite and gypsum, at sites in Tamil Nadu and Chile that resemble Martian environments.
About Melanterite
- Melanterite is a hydrated iron sulphate.
- It is formed through the oxidative weathering and decomposition of primary iron sulfide minerals, most commonly pyrite (FeS₂) or its unstable polymorph marcasite.
- It is often found in mines as a post-mining formation on mine walls.
- Properties:
- Colour: It is colorless to white or green, also greenish-blue to blue with increased copper content and colourless to pale green in transmitted light.
- Melanterite has conchoidal fracture and displays cleavage in two directions.
- It is highly soluble in water.
- Formula: Fe2+(H2O)6(SO4) · H2O
- Colour: It is colorless to white or green, also greenish-blue to blue with increased copper content and colourless to pale green in transmitted light.
- Recent findings: Melanterite has been detected in Neyveli, Tamil Nadu.
- It forms under temporary wet, acidic and oxidising conditions and provides evidence of short-lived water activity relevant to understanding Mars’ geological history.
About Gypsum
- Gypsum is a common sulfate mineral.
- It is found in large beds along with other evaporite minerals, especially in Permian and Triassic sedimentary formations.
- It is also found in salt pans and saline lakes and is a key part of cap rock on salt domes.
- Properties:
- Forms: It appears in various forms, including selenite (well-developed crystals), satin spar (fibrous, silky, and opalescent), alabaster (fine-grained and massive), and gypsite (earthy and pulverulent).
- Composition: It is composed of hydrated calcium sulfate.
- Colour: It is colourless to white, often tinged other hues due to impurities and colourless in transmitted light.
- Formulae: CaSO₄·2H₂O
- Applications: It is used as a fluxing agent, fertilizer, filler, and retarder in portland cement.
- When calcined, it becomes plaster of Paris, used in building materials.
- Leading Producers: Its deposits occur in many countries, but Spain, Thailand, the United States, Turkey, and Russia are among the leading producers.
- Recent findings: Gypsum is one of the two hydrous sulphate minerals identified in the Atacama Desert in Chile and the Tiruchirappalli Badlands, a semi-arid geological and palaeoclimatic region in Tamil Nadu.
- It records past water activity and can preserve potential biosignatures within its mineral structure, making it significant for astrobiological investigations.
