Hydroxylapatite ps. Vivianite (presumed)

Item Description

This is a very unusual specimen from a lesser-known mine located about 20 km southwest of the Ojuela Mine in Mexico. It features sculptural, dense clusters of bladed pale yellow pseudomorphs perched on smaller, flower-like shapes of hydroxylapatite pseudomorphs. The matrix is probably "collophane apatite," a rare variety of carbonate-rich apatite. The original mineral being replaced is still under debate, with possibilities including vivianite, hemimorphite, or gypsum. Regardless of its original form, this specimen is superbly unique, and I find great enjoyment in examining its intricate details. The dendritic pyrolusite coating, formed in the final stages, adds a painterly effect to the piece. This material was mined in the 1960s, and many specimens from Astillero have been mistakenly sold as originating from Ojuela (according to MINDAT). For further reference, see Page 54 of the Mineralogical Record Ojuela Mine Special Issue, 2003, Vol 34, No. 5. Ex Bill and Anne Cook, Jingnan (Tom) Zhang.