Herderite Explained

Herderite
Category:Phosphate mineral
Formula:CaBe(PO4)(F,OH)
Imasymbol:Hrd[1]
Strunz:8.BA.10
System:Monoclinic
Class:Prismatic (2/m)
(same H-M symbol)
Symmetry:P21/a
Unit Cell:a = 4.81, b = 7.7,
c = 9.82 [Å]; β = 90.1°; Z = 4
Colour:Colourless, pale yellow, greenish-white
Habit:Occurs as prismatic tabular crystals, pseudo-orthorhombic or pseudo-hexagonal; fibrous botryoidal to spheroidal aggregates
Twinning:On or as fishtail contact
Cleavage:Indistinct on
Fracture:Subconchoidal
Mohs:5 - 5.5
Lustre:Vitreous
Diaphaneity:Transparent - translucent
Gravity:3.02
Opticalprop:Biaxial (-)
Refractive:nα = 1.556 - 1.592 nβ = 1.578 - 1.610 nγ = 1.589 - 1.620
Birefringence:δ = 0.033
2V:Calculated: 70°
Fluorescence:Fluoresces violet under UV; cathodoluminesces and phosphoresces pinkish orange under X-rays
References:[2] [3]

Herderite is a phosphate mineral belonging to the apatite, phosphate group, with formula CaBe(PO4)(F,OH). It forms monoclinic crystals, often twinned and variable in colour from colourless through yellow to green. It forms a series with the more common hydroxylherderite, which has more hydroxyl ion than fluoride.

It is found in many parts of the world, often in pegmatites and associated with other apatite minerals.

It was first described in 1828 for an occurrence in the Sauberg Mine, Ore Mountains, Saxony, Germany. It was named for Saxon mining official Sigmund August Wolfgang von Herder (1776–1838).[4]

Notes and References

  1. Warr. L.N.. 2021. IMA–CNMNC approved mineral symbols. Mineralogical Magazine. 85. 3. 291–320. 10.1180/mgm.2021.43. 2021MinM...85..291W. 235729616. free.
  2. http://rruff.geo.arizona.edu/doclib/hom/herderite.pdf Handbook of Mineralogy
  3. http://www.webmineral.com/data/Herderite.shtml Herderite on Webmineral
  4. http://www.mindat.org/min-1876.html Herderite on Mindat.org