Figure 9.

(A) Absent borate. Ca²⁺ and PO₄^3– segregate to give apatite, leaving behind Mg²⁺ and SO₄^2- to form epsomite, (B), in the presence of BO₃^3–, Mg²⁺, BO₃^3– and PO₄^3– segregate to give lüneburgite, leaving behind Ca²⁺ and SO₄^2- to form gypsum. (C) The segregation of gypsum and lüneburgite is seen in laboratory experiments. (D) Lüneburgite samples from three locations on the modern Earth, Chile, Crimea, and (from the type-locality) Germany. Samples are courtesy of Renato Pagano and Robert Lavinsky (The Arkenstone, Richardson TX, https://www.irocks.com/), illustrating the importance of commercial and amateur “rock hounds” in the development of this science.