Keckite is a rare phosphate mineral typically found as brown to yellowish-brown fibrous aggregates or crusts. It primarily occurs as a secondary alteration product of primary phosphate minerals within complex granite pegmatites.

Hardness

4.5

Mohs

Luster

Dull

Streak

Yellow white

Transparency

Translucent

mineralrareFillowite Group family

Keckite

Hardness: 4.5
Luster: Dull
Streak: Yellow white
Transparency: Translucent

Is this keckite?

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 keckite with a known reference. Keckite 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: yellow white.
3
Read the luster
Hold the specimen under a strong light. Luster: dull.
4
Match the color range
Compare against the expected color range: brown, gray brown, yellow brown.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: fan shaped.

Often confused with

Keckite vs. its common look-alikes, and how to tell them apart in the field.

mineral

Rockbridgeite

Mohs 3.5-4.5

How to tell apart: Streak differs, so Keckite leaves yellow white, Rockbridgeite leaves greenish gray; luster reads dull on Keckite and vitreous to dull on Rockbridgeite.

How to tell apart: Keckite is noticeably harder (Mohs 4.5 vs. 3.5); streak differs, so Keckite leaves yellow white, Strengite leaves white; luster reads dull on Keckite and vitreous on Strengite.

Compare →

Often found alongside keckite

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

All properties

Chemical formula: CaMn²⁺₄Fe³⁺₂(PO₄)₄(OH)₄·2H₂O
Mohs hardness: 4.5
Density: 2.60 g/cm³
Colors: Brown Gray brown Yellow brown
Streak: Yellow white
Luster: Dull
Transparency: Translucent
Crystal system: Monoclinic
Crystal habit: Fan shaped
Cleavage: Poor on {001}, and poorer on {100}
Rarity: Rare
Uses: Collector
Host rock: A weathering product of phosphate minerals in a complex granite pegmatite

Where rockhounds find keckite

Classic worldwide localities

Bavaria, from Hagendorf, at the Silbergrube quarry, near Waidhaus, and at Hühnerkobel, near Zwiesel, Germany
Bendada pegmatite, near Guarda, Portugal

Field-hunting tip

Where it forms: A weathering product of phosphate minerals in a complex granite pegmatite. If you start seeing rockbridgeite, phosphophyllite, scholzite in float, you are in the right ground. Typical habit: fan shaped. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify keckite?+

Mohs hardness is 4.5. Luster: dull. The streak is yellow white. Common colors include brown, gray brown, yellow brown.

Where is keckite found?+

Notable localities include Bavaria, from Hagendorf, at the Silbergrube quarry, near Waidhaus, and at Hühnerkobel, near Zwiesel, Germany; Bendada pegmatite, near Guarda, Portugal.

What rocks look like keckite?+

Keckite is most often confused with Rockbridgeite, Strengite. A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with keckite?+

Keckite commonly co-occurs with Rockbridgeite, Phosphophyllite, Scholzite, Fairfieldite, Vivianite, Reddingite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does keckite form in?+

Where it forms: A weathering product of phosphate minerals in a complex granite pegmatite. Working float back to the host body is the standard way to chase a fresh occurrence.

What is keckite used for?+

Keckite is used in collector.

Find keckite on the map

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