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

4.5

Mohs

Luster

Vitreous

Streak

Greenish olive

Transparency

Opaque

mineralrarePumpellyite Group family

Julgoldite-(Mg)

Hardness: 4.5
Luster: Vitreous
Streak: Greenish olive
Transparency: Opaque

No image

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 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.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
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(Si₂O₇)(SiO₄)(OH)·H₂O
Mohs hardness: 4.5
Colors: Black Brownish black
Streak: Greenish olive
Luster: Vitreous
Transparency: Opaque
Crystal system: Monoclinic
Crystal habit: Tabular crystals, radiating aggregates
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: metamorphic manganese deposits

Where rockhounds find julgoldite-(mg)

Classic worldwide localities

Långban, Sweden
Sahara, Morocco

Field-hunting tip

Where it forms: metamorphic manganese deposits. If you start seeing hematite, calcite, andradite in float, you are in the right ground. Typical habit: tabular crystals, radiating aggregates. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify julgoldite-(mg)?+

Mohs hardness is 4.5. Luster: vitreous. The streak is greenish olive. Common colors include black, brownish black.

Where is julgoldite-(mg) found?+

Notable localities include Långban, Sweden; Sahara, Morocco.

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?+

Where it forms: 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

RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.