Julgoldite-(Fe²⁺)
Current inventory: 0 gems
 

  
Julgoldite-(Fe²⁺) was named in 1971 by Professor Paul B. Moore in honor of Professor Julian Royce Goldsmith (1918–1999), mineralogist and geochemist, University of Chicago, Chicago, Illinois, USA, and its ferrous iron content.

Discovered in 1971; IMA status: Valid (IMA Approved 1971)

Chemistry

Chemical Formula:

Ca₂(Fe²⁺,Mg)(Fe³⁺,Al)₂(Si₂O₇)(SiO₄)(OH)₂ • (H₂O)

Hydrated Calcium Iron Aluminum Silicate Hydroxide

Molecular Weight:

2,199.83 gm

Composition:

Calcium

14.57 %

Ca

20.39 %

CaO

Magnesium

0.22 %

Mg

0.37 %

MgO

Aluminum

1.35 %

Al

2.55 %

Al₂O₃

Iron

27.16 %

Fe

38.84 %

Fe₂O₃

Silicon

15.32 %

Si

32.78 %

SiO₂

Hydrogen

0.64 %

H

5.73 %

H₂O

Oxygen

40.73 %

O

100.00 %

100.65 %

= TOTAL OXIDE

Classification

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/C.24-60

Nickel-Strunz 10th Ed. ID:

9.BG.20

9 : SILICATES (Germanates)
B : Sorosilicates
G : Sorosilicates with mixed SiO₄ and Si₂O₇ groups; cations in octahedral [6] and greater coordination

Related to:

Pumpellyite Group. Julgoldite-(Fe²⁺)-Pumpellyite-(Fe²⁺) Series. Julgoldite-(Fe²⁺)-Pumpellyite-(Mg) Series.

Members of Group:

Pumpellyite Group: Julgoldite-(Fe²⁺), Julgoldite-(Fe³⁺), Julgoldite-(Mg), Okhotskite, Poppiite, Pumpellyite-(Al), Pumpellyite-(Fe²⁺), Pumpellyite-(Fe³⁺), Pumpellyite-(Mg), Pumpellyite-(Mn²⁺), Shuiskite 

Varieties:

None

Synonyms:

None

Crystal Data

Crystallography:

Monoclinic - Prismatic

Crystal Habit:

Crystals flat prismatic to bladed, to 2 mm, elongated along [010] and flattened || {100}. In fan-shaped, plumose crystal groups; granular.

Twinning:

Twin plane {001}, typically repeated, common.

Physical Properties

Cleavage:

Perfect on {100} and {001}

Fracture:

Conchoidal

Tenacity:

Brittle

Moh's Hardness:

4.5

Density:

3.58 - 3.60 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Optical Properties

Color:

Deep black, greenish black to green in small fragments; in thin section, brilliant interference colors in greens or blues

Transparency:

Opaque

Luster:

Nearly submetallic

Refractive Index:

1.776 - 1.836  Biaxial ( - )

Birefringence:

0.060

Dispersion:

n/a

Pleochroism:

Strong; X = pale brown; Y = pale brownish green; Z = deep emerald-green

Occurances

Geological Setting:

In Hematite-Magnetite ore (Långban, Sweden); in Quartz-diabase (Scotland)

Common Associations:

Apophyllite, Barite, Hematite, Magnetite, Ilvaite, Calcite, Quartz, Chlorite, Prehnite, Epistilbite, Stilbite, Pectolite, Laumontite, Babingtonite, Titanite

Common Impurities:

n/a

Type Locality:

Långban, Filipstad, Värmland, Sweden

Year Discovered:

1971

View mineral photos:

Julgoldite-(Fe²⁺) Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Julgoldite-(Fe²⁺) is a sorosilicate mineral and a member of the Pumpellyite Group of minerals that also includes Pumpellyite-(Mg), also called Chlorastrolite. Julgoldite crystals are typically deep black, flat, prismatic to bladed, to 2 mm, often in fan-shaped, plumose crystal groups with nearly submetallic luster. The crystals are usually quite small but can be very attractive as specimens or druzy style cabochons showing groups of minute deep black Julgoldite crystals on pinkish Heulandite crystals (see picture above). Probably the best source of these is Nasik, Maharashtra, India.

Julgoldite-(Fe²⁺) was named in 1971 by Professor Paul B. Moore in honor of Professor Julian Royce Goldsmith (1918–1999), mineralogist and geochemist, University of Chicago, Chicago, Illinois, USA, and its ferrous iron content.

Julgoldite-(Fe²⁺) distribution: At Långban, Filipstad, Värmland, Sweden. Between Tafjord and Fjøra, Sunnmøre district, Norway. In the Ratho quarry, near Edinburgh, and the Auchinstarry quarry, Kilsyth, Scotland. In Germany, from the WolfmÄuhl quarry, Waldgrehweiler, Rhineland-Palatinate. From Hale Creek, Trinity County, California, and in the Clark mine, Copper Harbor, Keweenaw County, Michigan, USA. At Sawda, near Jalgoan, and Bombay, Maharashtra, India. In the Marlin Norite quarry, Bushveld complex, South Africa.
 

  
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