reaction rim

reaction rim

[rē′ak·shən ‚rim]
(petrology)
A surficial rim around one mineral produced by the reaction of the core mineral with the surrounding magma. Also known as reaction border.
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References in periodicals archive ?
Grains with preserved reaction rims have not been transported any great distance.
Observations of reaction rims and shagreen texture indicate the kimberlite minerals are derived from a local and potentially diamond-bearing kimberlite source(s).
A large population of the kimberlite mineral grains contained preserved reaction rims demonstrating that down ice movement of the grains from source material was limited.
The morphology of grains, commonly preserved reaction rims and proximity to deep seated structures, all point to a local source.