Assertion: valuable mineral | /r/AtLocation | layer
Facets:
value: in mineral grains
type: LOCATION
Source sentences:
text: Targets are divided into two general categories of materials: placer deposits, consisting of valuable minerals contained within river gravels, beach sands, and other unconsolidated materials; and lode deposits, where valuable minerals are found in veins, in layers, or in mineral grains generally distributed throughout a mass of actual rock.