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Herderite
Current inventory:  2 gems
 

Chemistry:  CaBe(PO₄)F  or  CaBe[(F,OH)|PO₄]

Discovered in 1828;   IMA status: Valid (pre-IMA; Grandfathered).
Herderite is named after Sigmund August Wolfgang von Herder (1776-1838), a mining official in Freiburg, Saxony, Germany.

Classification

Mineral Classification:

Phosphates

Strunz 8th Ed. ID:

7/B.01-10

Nickel-Strunz 10th Ed. ID:

8.BA.10

8 : PHOSPHATES, ARSENATES, VANADATES
B : Phosphates, etc., with additional anions, without H₂O
A : With small and medium-sized cations

Related to:

Herderite-Hydroxylherderite Series. The Fluorine-dominant analogue of Hydroxylherderite. Herderite is isotypic with Datolite.

Crystal Data

Crystallography:

Monoclinic - Prismatic

Crystal Habit:

Stout prismatic crystals, thick tabular. Commonly pseudo-orthorhombic in aspect, rarely monoclinic; pseudo-hexagonal at times. Also occurs as botryoidal or spheroidal aggregates with a radial-fibrous structure.

Twinning:

On [100] or [001] as fishtail contact. Most crystals are twinned; however, some exhibit no outward signs of this morphology.

Physical Properties

Cleavage:

Imperfect, Fair; [110] Interrupted

Fracture:

Sub-Conchoidal

Tenacity:

Brittle

Hardness (Mohs):

5.0 - 5.5

Density:

2.95 - 3.02 (g/cm³)

Luminescence:

Fluoresces violet under UV; cathodoluminesces and phosphoresces pinkish orange under X-rays.

Radioactivity:

Not Radioactive

Optical Properties

Color:

Colorless, pale Yellow, Yellowish Green, light Green

Transparency:

Transparent to Translucent

Luster:

Vitreous

Refractive Index:

1.556 - 1.620  Biaxial ( - )

Birefringence:

0.033

Dispersion:

Moderate; r > v; 0.017

Pleochroism:

None

Occurances

Geological Setting:

Complex granitic pegmatites.

Common Associations:

n/a

Type Locality:

Sauberg Mine, Ehrenfriedersdorf, Erzgebirge, Saxony, Germany

Year Discovered:

1828

View mineral photos:

Herderite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Herderite is a very rare phosphate collectors gem. It is a very attractive gem but too soft for jewelry ware. It is found in many colors; yellow, green, blue, pink, pale violet and colorless. Currently, most material is from Brazil, although it is found in several localities around the world including pale yellow crystals from Maine, USA. The most notable occurances of gem quality crystals are Minas Gerais, Brazil and Skardu District, Baltistan, Northern Areas, Pakistan.
 

  
Herderite gems for sale: