The mineral was named after Leo Strippelmann, who was director of the salt works at Westeregeln in Germany.

[5] In the mineral family of leonite, the lattice contains sulfate tetrahedrons, a divalent element in an octahedral position surrounded by oxygen, and water and univalent metal (potassium) linking these other components together.

[6] The divalent metal cation (magnesium) is embedded in oxygen octahedra, four from water around the equator, and two from sulfate ions at the opposite poles.

In the next form at lower temperatures, the disordered sulfate appears in two different orientations giving the sequence OAOBOAOBOAOBOAOB.

[6] The c dimension and unit cell volume are doubled due to the presence of four sulfate layers rather than two as in the other forms.

[14] The infrared spectrum of sulfate stretching modes shows peaks in absorption at 1005, 1080, 1102, 1134 and 1209 cm−1.

[15] Starting in 1897, Jacobus Henricus van 't Hoff investigated how different salts were formed as sea water evaporated in different conditions.

[18] In salt (NaCl) saturated brine, leonite can be deposited from magnesium and potassium sulfate mixtures as low as 25 °C.

The 25 °C isotherm of the system has leonite surrounded by sylvine, picromerite, astrakanite, epsomite, and kainite.

[19] Leonite is precipitated in series solar ponds at the Great Salt Lake.

Leonite can be a minor primary constituent of evaporite potash deposits, or a secondary mineral.

[29] Leonite was first found in nature in the Stassfurt Potash deposit, Westeregeln, Egeln, Saxony-Anhalt, Germany.

[2] Outside Germany, it is found at Vesuvius, Italy; Stebnyk, Ukraine; and the Carlsbad potash district, Eddy County, New Mexico, US.

It is found in crystalline speleothems in Tăuşoare Cave in Romania; here it occurs with konyaite (K2Mg(SO4)2·5H2O), syngenite (K2Ca(SO4)2·H2O), thenardite (Na2SO4), and mirabilite (Na2SO4·10H2O).

[31] Leonite also occurs in Wooltana Cave, Flinders Ranges, South Australia.

The filtrate is concentrated by evaporation, where more leonite crystallises, which is then recycled to the start of the process, adding more langbeinite or picromerite.

[25] Leonite may have been used in an alchemical formula to make "potable gold" around 300 AD in China.