Editing Tuff (section)

====Kimberlites====
Occurrences of ultramafic tuff include surface deposits of [[kimberlite]] at [[maar]]s in the [[diamond]]-fields of southern Africa and other regions. The principal variety of kimberlite is a dark bluish-green, serpentine-rich breccia (blue-ground) which, when thoroughly oxidized and weathered, becomes a friable brown or yellow mass (the "yellow-ground").<ref name=EB1911/> These breccias were emplaced as gas–solid mixtures and are typically preserved and mined in [[diatreme]]s that form intrusive pipe-like structures. At depth, some kimberlite breccias grade into root zones of dikes made of unfragmented rock. At the surface, ultramafic tuffs may occur in maar deposits. Because kimberlites are the most common igneous source of diamonds, the transitions from maar to diatreme to root-zone dikes have been studied in detail. Diatreme-[[facies]] kimberlite is more properly called an ultramafic breccia rather than a tuff.