Misnamed Scoria - ACtually Clinkers
"When lignite beds burn, they harden, sinter (sintering is a process that fuses material into a hard mass, without melting it), or sometimes they melt the overlying and surrounding rocks. The baking process colors the nearby materials dominantly red, but shades of black, gray, purple, yellow, and other hues are common too.nn13f4.jpg (271516 bytes) The intensity of the colors depends on the mineral composition and grain size of the material that was baked and also on how hot a temperature was reached during the baking process. The reddish color, which is most common, is due primarily to the presence of the mineral hematite (iron oxide, the same as common rust). The intensity of the colors of clinker also vary depending on whether the material is dry or wet. After a shower, the clinker is typically much brighter red than when it is dry." "North Dakota's Clinker." North Dakota's Clinker. N.p., n.d. Web. 20 Nov. 2015. <https://www.dmr.nd.gov/ndgs/ndnotes/ndn13_h.htm>.