Jahnsite-(MnMnZn) is a rare phosphate mineral found in phosphate-rich granite pegmatites. Collectors typically look for small, sharp, yellow to brown tabular crystals lining cavities in weathered phosphate nodules.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineralrareJahnsite Group family

Jahnsite-(MnMnZn)

Hardness: 4
Luster: Vitreous
Streak: White
Transparency: Translucent

Is this jahnsite-(mnmnzn)?

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 jahnsite-(mnmnzn) with a known reference. Jahnsite-(MnMnZn) sits at Mohs 4 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Jahnsite-(MnMnZn) leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Jahnsite-(MnMnZn) typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: yellow, yellow-brown, brown.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: tabular crystals, drusy coatings.

Often confused with

Jahnsite-(MnMnZn) vs. its common look-alikes — and how to tell them apart in the field.

Often found alongside jahnsite-(mnmnzn)

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

All properties

Chemical formula: CaMn²⁺Mg₂Zn₂(PO₄)₄(OH)₂·8H₂O
Mohs hardness: 4
Density: 2.8-2.9 g/cm³
Colors: Yellow Yellow-brown Brown
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Tabular Crystals, Drusy Coatings
Cleavage: Poor
Rarity: Rare
Uses: Collector
Host rock: Granite Pegmatites
Typical price: $50-300 per specimen

Where rockhounds find jahnsite-(mnmnzn)

Classic worldwide localities

Tip Top Mine, South Dakota, USA
Palermo No. 1 Mine, New Hampshire, USA

Field-hunting tip

Look in granite pegmatites country — that is the host setting where jahnsite-(mnmnzn) typically forms. If you start seeing rockbridgeite, triphylite, phosphosiderite in float, you are in the right ground. Field specimens usually show a tabular crystals, drusy coatings habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify jahnsite-(mnmnzn)?+

Mohs hardness is 4. It typically shows a vitreous luster. The streak is white. Common colors include yellow, yellow-brown, brown.

Where is jahnsite-(mnmnzn) found?+

Notable localities include Tip Top Mine, South Dakota, USA; Palermo No. 1 Mine, New Hampshire, USA.

How much is jahnsite-(mnmnzn) 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 rocks look like jahnsite-(mnmnzn)?+

Jahnsite-(MnMnZn) is most often confused with Jahnsite-(CaMnMg). A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with jahnsite-(mnmnzn)?+

Jahnsite-(MnMnZn) commonly co-occurs with Rockbridgeite, Triphylite, Phosphosiderite, Hureaulite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does jahnsite-(mnmnzn) form in?+

Jahnsite-(MnMnZn) typically forms in granite pegmatites. Working float back to the host body is the standard way to chase a fresh occurrence.

What is jahnsite-(mnmnzn) used for?+

Jahnsite-(MnMnZn) is used in collector.

Find jahnsite-(mnmnzn) on the map

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