Julgoldite-(Mg) is a rare member of the pumpellyite group found in specialized metamorphic environments. Collectors should look for dark, tabular crystals or radiating sprays typically occurring in association with manganese-rich mineral suites.

Hardness

Mohs

Luster

Vitreous

Streak

Brownish

Transparency

Opaque

mineralrarePumpellyite Group family

Julgoldite-(Mg)

Hardness: 6
Luster: Vitreous
Streak: Brownish
Transparency: Opaque

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Is this julgoldite-(mg)?

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-(mg) with a known reference. Julgoldite-(Mg) sits at Mohs 6 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Julgoldite-(Mg) leaves a brownish streak.
3
Read the luster
Hold the specimen under a strong light. Julgoldite-(Mg) typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: black, brownish black.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: tabular crystals, radiating aggregates.

Often found alongside julgoldite-(mg)

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

All properties

Chemical formula: Ca₂MgFe²⁺Fe³⁺(Si₂O₇)(SiO₄)(OH)₂·H₂O
Mohs hardness: 6
Density: 3.55 g/cm³
Colors: Black Brownish Black
Streak: Brownish
Luster: Vitreous
Transparency: Opaque
Crystal system: Monoclinic
Crystal habit: Tabular Crystals, Radiating Aggregates
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Metamorphic Manganese Deposits
Typical price: $50-300 per specimen

Where rockhounds find julgoldite-(mg)

Classic worldwide localities

Långban, Sweden
Sahara, Morocco

Field-hunting tip

Look in metamorphic manganese deposits country — that is the host setting where julgoldite-(mg) typically forms. If you start seeing hematite, calcite, andradite in float, you are in the right ground. Field specimens usually show a tabular crystals, radiating aggregates habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify julgoldite-(mg)?+

Mohs hardness is 6. It typically shows a vitreous luster. The streak is brownish. Common colors include black, brownish black.

Where is julgoldite-(mg) found?+

Notable localities include Långban, Sweden; Sahara, Morocco.

How much is julgoldite-(mg) worth?+

Typical asking prices fall in the range of $50-300 per specimen. Quality, size, and provenance can move individual specimens well outside that range.

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

Julgoldite-(Mg) commonly co-occurs with Hematite, Calcite, Andradite. Spotting any of these in float or country rock is a useful trip signal.

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

Julgoldite-(Mg) typically forms in metamorphic manganese deposits. Working float back to the host body is the standard way to chase a fresh occurrence.

What is julgoldite-(mg) used for?+

Julgoldite-(Mg) is used in collector.

Find julgoldite-(mg) on the map

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