Danalite

Discovered in 1866; IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

Fe²⁺₄Be₃(SiO₄)₃S

Iron Beryllium Silicate Sulfide

Molecular Weight:

558.74 gm

Composition:

Beryllium

4.84 %

Be

13.43 %

BeO

Iron

39.98 %

Fe

51.43 %

FeO

Silicon

15.08 %

Si

32.26 %

SiO₂

Sulfur

5.74 %

S

5.74 %

S^2-

—

 —  %

S

-2.86 %

-O=S

Oxygen

34.36 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/J.12-10

Nickel-Strunz 10th Ed. ID:

9.FB.10

9 : SILICATES (Germanates)
F : Tektosilicates without zeolitic H₂O
B : Tektosilicates with additional anions

Related to:

Helvine Group. Danalite-Genthelvite Series. Danalite-Helvine Series.

Members of Group:

Helvine Group: Danalite, Genthelvite, Helvine, Tugtupite

Varieties:

None

Synonyms:

ICSD 201639, PDF 11-491

Crystal Data

Crystallography:

Isometric - Hextetrahedral

Crystal Habit:

As octahedral and dodecahedral crystals, to 10 cm; as irregular segregations.

Twinning:

None

Physical Properties

Cleavage:

Poor/indistinct; poor on {111} 

Fracture:

Irregular/uneven, sub-conchoidal

Tenacity:

Brittle

Mohs Hardness:

5.5 - 6.0

Density:

3.28 - 3.26 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Optical Properties

Color:

Yellow, pink, reddish brown, red; colorless to pink in thin section.

Transparency:

Translucent to semi-transparent

Luster:

Vitreous, Greasy

Refractive Index:

1.747 - 1.771  Isotropic

Birefringence:

0.000 - Isotropic minerals have no birefringence

Dispersion:

n/a

Pleochroism:

None

Occurances

Geological Setting:

In granites, granite pegmatites, zones of contact metamorphism, skarns, and gneisses.

Common Associations:

Magnetite, Garnet, Fluorite (skarn); Albite, Cassiterite, Pyrite, Muscovite (tin-bearing pegmatites); Arsenopyrite, Quartz, Chlorite (hydrothermal deposits)

Common Impurities:

Mn, Zn, Ca, S

Type Locality:

Rockport, Essex Co., Massachusetts, USA

Year Discovered:

1866

View mineral photos:

Danalite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Danalite is a rare beryllium silicate sulfide mineral that is a member of the Helvine Group of minerals that also includes Genthelvite, Helvine and Tugtupite. Danalite was first described in 1866 from a deposite in Essex County, Massachusettes, USA. Danalite can be found in colors of yellow, pink, reddish brown or red but seldom crystalized and most often found as red to pink opaque masses in rock. Danalite is translucent to semi-transparent with vitreous to greasy luster and a Mohs hardness of 5.5 - 6.0. Faceted gems are very rare and typically very small.

Danalite was named in 1866 by Harvard mineralogist and chemist Josiah Parsons Cooke Jr. (1827-1894) to honor American geologist, mineralogist, volcanologist, and zoologist James Dwight Dana (1813-1895). Dana is credited with naming more than 100 minerals. He also published more than 200 titles of books, manuscripts and papers beginning in 1835 with a paper on the conditions of Mount Vesuvius. Dana's best known books were his System of Mineralogy (1837), Manual of Mineralogy (1848) and Manual of Geology (1863). These books are very well known in the fields of mineralogy and geology. The Manual of Mineralogy became a standard college text and has been continuously revised and updated. The 23rd edition is now in print under the title Manual of Mineral Science (Manual of Mineralogy) (2007). Dana's System of Mineralogy has also been continuously revised and updated with the 8th edition being published in 1997 under the title Dana's New Mineralogy.

Danalite can be found at the following localities: in the USA, at Rockport and Gloucester, Essex County, Massachusetts; on Moat Mountain, Conway, Carroll County, New Hampshire; at Iron Mountain, Sierra County, New Mexico; and from the Black Hills, south of Jerome, Yavapai County, Arizona. From Needlepoint Mountain, McDame area, British Columbia, and on Walrus Island, James Bay, Quebec, Canada. In Sweden, from Yxsjö, Örebro. At Redruth, St. Just, Lanlivery, Falmouth, and Lanivet, Cornwall, England. In Russia, from Imalka, Transbaikal, and other less-well-defined localities. From the Kara mine, Tasmania, and on Mt. Francisco, Ribawa area, Western Australia. In the Mihara mine, Hiroshima Prefecture, Japan.

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