What is Herderite?
Herderite is a calcium beryllium phosphate from granitic pegmatites, forming pale prismatic crystals that may be yellow, green or colourless.
Mineralogy and structure
Reference formula: CaBePO4(F,OH). Herderite forms a fluorine-hydroxyl series with hydroxylherderite. Beryllium-bearing material should be treated as a labelled display specimen rather than cut or powdered casually. Herderite belongs to the phosphates and has a monoclinic crystal system. Typical hardness is 5–5.5 on the Mohs scale and specific gravity is approximately 2.9–3.0.
Colour and appearance
Typical colours include colourless, white, yellow, green. The usual prismatic, tabular, granular habit and vitreous lustre are useful descriptive features, but colour alone is not diagnostic.
Formation and localities
Herderite forms in or is associated with granitic pegmatites and late-stage phosphate-rich pockets. Important documented localities include Brazil, Germany, Portugal, the United States, Pakistan and Madagascar.
Collecting and care
Avoid cutting, grinding and dust; protect clear crystals and retain pegmatite provenance.
