SAPONITE (Ca0.5,Na)0.3(Mg,Fe)3(Si,Al)4O10(OH)2·4H2O (monoclinic)
smectite group; varieties: griffithite, medmontite, sobotkite

variety medmontite, mottled green-tan-olive chalky
Copper King Mine, Copper Spur, Boulder County, Colorado