Hydroxylherderite
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Hydroxylherderite was named "Hydro-Herderite" in 1894 by Samuel L. Penfield. The name was changed to "Hydroxyl-Herderite" by Palache, Berman, and Frondel in 1954. It was originally named for Siegmund August Wolfgang von Herder (1776-1838), Mining official in Freiberg, Germany. The "Hydroxyl-" prefix signifies the dominance of hydroxide over fluorine.

Discovered in 1894; IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

CaBe(PO₄)(OH)

Calcium Beryllium Phosphate Hydroxide

Molecular Weight:

161.07 gm

Composition:

Calcium

24.88 %

Ca

34.82 %

CaO

Beryllium

5.60 %

Be

15.53 %

BeO

Phosphorus

19.23 %

P

44.06 %

P₂O₅

Hydrogen

0.63 %

H

5.59 %

H₂O

Oxygen

49.67 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Phosphates

Strunz 8th Ed. ID:

2/D.17-120

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 hydroxyl-dominant analogue of Herderite. Isotypic with Datolite.

Varieties:

None

Synonyms:

Hydro-fluorherderite, Hydro-herderite, ICSD 67601, PDF 34-147

Crystal Data

Crystallography:

Monoclinic - Prismatic

Crystal Habit:

As stout prismatic crystals, elongated along [001] or [100], may be thick tabular {001}, typically with complex but rounded form development, to 17 cm; botryoidal to spherical, radial fibrous, in aggregates.

Twinning:

On {100} or {001} or both, as “fishtail” contact twins, common 

Physical Properties

Cleavage:

Poor/Indistinct on {110}

Fracture:

Irregular/Uneven

Tenacity:

Brittle

Moh's Hardness:

5.0 - 5.5

Density:

2.95 (g/cm³)

Luminescence:

May fluoresce weak yellow under SW UV, sometimes with bright yellow-orange phosphorescence.

Radioactivity:

Not Radioactive

Other:

Soluble in acids

Optical Properties

Color:

Colorless, gray, brown, pale yellow, greenish white, light blue, purple; colorless in transmitted light; may be blue-green or blue in daylight, lavender or light violet in incandescent light.

Transparency:

Transparent to translucent

Luster:

Vitreous to subvitreous, resinous

Refractive Index:

1.589 - 1.643  Biaxial ( - )

Birefringence:

0.030

Dispersion:

r > v, inclined

Pleochroism:

None

Occurances

Geological Setting:

A late-stage mineral in miarolitic cavities in complex granite pegmatites, of hydrothermal or probable pneumatolytic origin; may form from the alteration of beryl or beryllonite.

Common Associations:

Elbaite, Topaz, Cassiterite, Albite, Microcline, Muscovite, Lepidolite, Quartz

Common Impurities:

n/a

Type Locality:

Paris, Maine, USA

Year Discovered:

1894

View mineral photos:

Hydroxylherderite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Hydroxylherderite is a rare calcium beryllium phosphate mineral that typically occurs in pegmatite deposits as small, unimpressive crystals in a variety of colors including gray, brown, pale yellow, greenish white, light blue, purple and colorless. Hydroxylherderite is the hydroxyl-dominant analogue of Herderite. Most specimens labelled "Herderite" are in fact Hydroxylherderite.

Hydroxylherderite was named "Hydro-Herderite" in 1894 by Samuel L. Penfield. The name was changed to "Hydroxyl-Herderite" by Palache, Berman, and Frondel in 1954 and renamed Hydroxylherderite by Mineralogical Record (v39, 2008, p131). It was originally named for Siegmund August Wolfgang von Herder (1776-1838), Mining official in Freiberg, Germany. The "Hydroxyl" prefix signifies the dominance of hydroxide over fluorine.

Locations for Hydroxylherderite: Many localities, but uncommon at most. Some for analyzed material include: in the USA, in Maine, at Paris, Hebron, Greenwood, Stoneham, and Newry, Oxford County, at Topsham, Sagadahoc County, Poland and Auburn, Androscoggin County, and elsewhere; in the Fletcher and Palermo #1 mines, near North Groton, Grafton County, and at the Keyes mine, Orange, Grafton County, New Hampshire; from the Blue Chihuahua pegmatite, near Oak Grove, San Diego County, California. In Germany, at the Epprechtstein and Waldheim quarries, Fichtelgebirge, Bavaria. In the Viitaniemi pegmatite, near Eräjärvi, Finland. From Mursinsk, Ural Mountains, Russia. At Ungursuay, Kazakhstan. In Brazil, large crystals from the Xandá mine, Virgem da Lapa, and at the Golconda mine, near Governador Valadares, Minas Gerais.
 

  
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