Engelhauptite was approved by IMA with no 2013-009. Former name was UM (unknown mineral) K-Cu-Al-Cl-Vanadanate if you read older literature. Engelhauptite is linked to Volborthite with identical molecular structure [Cu3(V2O7)(OH)2]. If the channels of Volborthite in between are filled with H2O here at Engelhauptite they be taken with K and Cl anions. Thatr means the chemical content is different. (quote and thanks to G.Blaß)
Engelhauptite was found first time at volcano Kahlenberg "Auf'm Kopp" near Neroth, Eifel, Germany. In paragenetic with high content of Cu most items contents also Allophane/Chrysocolla, Wulfenite, yellow Volborthite and also Malachite. For more details and all EDX values please look in Eifel-CD by G. Blaß.
Items of Engelhauptite are very rare, best ones contains flowers of yellow orange crystals, other have only some small clusters of crystals 0.12 mm.