Commodity Code

chert

http://resource.geosciml.org/classifier/cgi/commodity-code/chert

definition Chert is a fine-grained silica-rich microcrystalline, cryptocrystalline or microfibrous sedimentary rock that may contain small fossils. It varies greatly in color (from white to black), but most often manifests as gray, brown, grayish brown and light green to rusty red; its color is an expression of trace elements present in the rock, and both red and green are most often related to traces of iron (in its oxidized and reduced forms respectively). more like this
notation
01.02.37.01 more like this
Chrt more like this
source http://en.wikipedia.org/wiki/Chert more like this
type
Resource
Concept
broader silica
narrower chert
in scheme commodity code
is primary topic of chert