Julgoldite-(Fe2+) is a rare member of the pumpellyite group, typically occurring as dark, small crystals in metamorphic environments. It is best identified by its deep black color and association with iron-rich mineral assemblages in specific manganese-bearing deposits. Collectors typically acquire this mineral as rare, micro-crystalline specimens from classic Swedish or North American localities.

Hardness

4.5

Mohs

Luster

Nearly submetallic

Streak

Greenish olive with a bluish tinge

Transparency

Transparent

mineralrarePumpellyite Group family

Julgoldite-(Fe2+)

Hardness: 4.5
Luster: Nearly submetallic
Streak: Greenish olive with a bluish tinge
Transparency: Transparent

Is this julgoldite-(fe2+)?

5-step field check

Run through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.

1
Test the hardness
Try to scratch julgoldite-(fe2+) with a known reference. Julgoldite-(Fe2+) sits at Mohs 4.5, softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Streak: greenish olive with a bluish tinge.
3
Read the luster
Hold the specimen under a strong light. Luster: nearly submetallic.
4
Match the color range
Compare against the expected color range: deep black, greenish black, green in small fragments.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: tabular crystals, radiating aggregates, massive.

Often confused with

Julgoldite-(Fe2+) vs. its common look-alikes, and how to tell them apart in the field.

mineral

Epidote

Mohs 6-7

How to tell apart: Epidote is the harder of the two (Mohs 6-7 vs. 4.5); streak differs, so Julgoldite-(Fe2+) leaves greenish olive with a bluish tinge, Epidote leaves grayish white; luster reads nearly submetallic on Julgoldite-(Fe2+) and vitreous, pearly, somewhat resinous on Epidote.

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Often found alongside julgoldite-(fe2+)

Minerals reported to co-occur with julgoldite-(fe2+). Spotting these in float or country rock is a strong cue you are in the right ground.

All properties

Chemical formula: Ca₂FeFe₂(Si₂O₇)(SiO₄)(OH)₂·H₂O
Mohs hardness: 4.5
Density: 3.58-3.60 g/cm³
Colors: Deep blackGreenish blackGreen in small fragments
Streak: Greenish olive with a bluish tinge
Luster: Nearly submetallic
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Tabular crystals, radiating aggregates, massive
Cleavage: Perfect on {100} and {001}
Rarity: Rare
Uses: Collector
Host rock: In hematite-magnetite ore (Långban, Sweden); in quartz-diabase (Scotland)

Where rockhounds find julgoldite-(fe2+)

Classic worldwide localities

Hale Creek, Trinity Co., California, and in the Clark mine, Copper Harbor, Keweenaw Co., Michigan, USA
Långban, Värmland, Sweden
Between Tafjord and Fjøra, Sunnmøre district, Norway
Ratho quarry, near Edinburgh, and the Auchinstarry quarry, Kilsyth, Scotland
Wolfmühl quarry, Waldgrehweiler, Rhineland-Palatinate, Germany
Sawda, near Jalgoan, and Bombay, Maharashtra, India

Field-hunting tip

Where it forms: In hematite-magnetite ore (Långban, Sweden); in quartz-diabase (Scotland). If you start seeing apophyllite, barite, hematite in float, you are in the right ground. Typical habit: tabular crystals, radiating aggregates, massive. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify julgoldite-(fe2+)?+

Mohs hardness is 4.5. Luster: nearly submetallic. The streak is greenish olive with a bluish tinge. Common colors include deep black, greenish black, green in small fragments.

Where is julgoldite-(fe2+) found?+

Notable localities include Hale Creek, Trinity Co., California, and in the Clark mine, Copper Harbor, Keweenaw Co., Michigan, USA; Långban, Värmland, Sweden; Between Tafjord and Fjøra, Sunnmøre district, Norway; Ratho quarry, near Edinburgh, and the Auchinstarry quarry, Kilsyth, Scotland; Wolfmühl quarry, Waldgrehweiler, Rhineland-Palatinate, Germany.

What rocks look like julgoldite-(fe2+)?+

Julgoldite-(Fe2+) is most often confused with Epidote. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with julgoldite-(fe2+)?+

Julgoldite-(Fe2+) commonly co-occurs with Apophyllite, Barite, Hematite, Magnetite, Ilvaite, Calcite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does julgoldite-(fe2+) form in?+

Where it forms: In hematite-magnetite ore (Långban, Sweden); in quartz-diabase (Scotland). Working float back to the host body is the standard way to chase a fresh occurrence.

What is julgoldite-(fe2+) used for?+

Julgoldite-(Fe2+) is used in collector.

Find julgoldite-(fe2+) on the map

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