Dictionary of Gems and Gemology

2009 Edition
| Editors: Mohsen Manutchehr-Danai

crust

Reference work entry
DOI: https://doi.org/10.1007/978-3-540-72816-0_5461

a surface soil layer may slightly cemented with silica, calcium carbonate, or iron oxide which becomes harder than the underlying horizon.

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© Springer-Verlag Berlin Heidelberg New York 2009