Pinpointing Float and Collecting Samples

So your at a claim, or wash river or some other spot where, erosion, eluvial or alluvial geology presents plenty of quartz, or mineralized limestone “float” (loose,down stream from source) rock to sample. What are the most efficient methods to collect and identify samples in the field, and best preserve them for rough estimate of visible gold or even detailed assay of the sample to identify the full gold content. The significance in understanding the full sample characteristics is important because it may help lead to value potential as well as tell you where to look for the source.