USGS - science for a changing world

Mineral Resources On-Line Spatial Data

National Geochemical Survey database

Frequently asked questions

  1. Some of the chemical analyses show negative values. What does this mean?
    Negative values indicate a determination that is below the limit of detection for the analytic method used. The magnitude of the negative number indicates the detection limit. For example, -10 ppm means the result should be regarded as < 10 ppm.

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