Regur (Black Cotton Soil)
Definition
Indian Vertisol formed on Deccan basalt. High in smectite (montmorillonite) clay, deep black colour, swells and shrinks dramatically with moisture. Major signature on shoes and clothing in central and western Indian casework.
- Parent rock
- Deccan basalt
- Dominant clay
- Smectite (montmorillonite)
- Colour
- Deep black
- Behaviour
- Swells and shrinks dramatically with moisture
- Region
- Central and western India
Common questions
Why is regur soil particularly useful as trace evidence in Indian casework?+
Its distinctive high smectite content, deep black colour, and marked shrink-swell behaviour make it recognisable and distinguishable from other Indian soil types under microscopic and mineralogical examination, so its presence on footwear or clothing can help place a person on the Deccan basalt terrain.
Does regur's shrink-swell property affect how the soil sample should be collected and stored for analysis?+
Yes, because the clay's volume changes with moisture content, samples should be collected and stored in a way that preserves their field moisture state where possible, since drying or rewetting can alter the physical characteristics an examiner might otherwise compare to a control sample.
Related terms
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- Loss on Ignition (LOI)
- Weight loss after heating dried soil to 550 degrees Celsius. Approximates the organic matter content. A simple, cheap, high-yield discriminator in field...
- Munsell Soil Colour
- Standardised colour notation written as hue, value and chroma (e.g. 10YR 4/3 dark brown). Read by holding a moist soil sample against...
- Soil
- Weathered surface layer of earth made of mineral particles, organic matter (humus), water, air and living micro-organisms. The forensic interest is in...
- USDA Texture Triangle
- Ternary diagram that classifies soils by relative proportion of sand (2.0 to 0.05 mm), silt (0.05 to 0.002 mm) and clay (less...
- XRD
- X-ray diffraction. Identifies crystalline mineral phases (quartz, feldspar, kaolinite, montmorillonite, calcite) by their characteristic d-spacings via Bragg's law. The mineral assemblage is...
- XRF and ICP-MS
- Elemental techniques for the trace-metal fingerprint (Fe, Ti, Mn, Cr, Ni, V, rare earths). XRF (often EDXRF) is non-destructive; ICP-MS is destructive...