Zykaite or zýkaite is a grey-white mineral consisting of arsenic, hydrogen, iron, sulfur and oxygen with formula: Fe3+4(AsO4)3(SO4)(OH)·15(H2O).

[1] This dull mineral is very soft with a Mohs hardness of only 2 and a specific gravity of 2.5.

Its common associates include limonite, gypsum, scorodite, quartz and arsenopyrite.

[2] It is found in the Czech Republic, New Zealand, Poland and Germany.

[3] Zykaite was first described in 1978 for an occurrence in the Safary mine, Kutná Hora, Bohemia, Czech Republic and named in honour of Vaclav Zyka (born 1926), a Czech geochemist.