A black layer of accumulated dirt
... cleaned before 
cooking, leeks must be topped and tailed (roots discarded, dark-green parts 
removed),... [DOC] [TLE] Caliche - Wikipedia [PAR] Caliche is a sedimentary rock, a hardened natural cement of calcium carbonate 
that binds other ... Caliche generally forms when minerals leach from the upper 
layer of the soil (the A horizon) and accumulate in the next layer (the B horizon), 
at depths of approximately three to 10 feet under the surface.