Arrojadite-(KFe) is a complex phosphate mineral primarily found in granitic pegmatites. Collectors usually find it as massive, olive-green aggregates rather than well-defined crystals, making accurate identification often reliant on chemical analysis or X-ray diffraction.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrareArrojadite Group family

Arrojadite-(KFe)

Hardness: ~5
Luster: Vitreous
Streak: White
Transparency: Transparent

Is this arrojadite-(kfe)?

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 arrojadite-(kfe) with a known reference. Arrojadite-(KFe) sits at Mohs ~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: white.
3
Read the luster
Hold the specimen under a strong light. Luster: vitreous.
4
Match the color range
Compare against the expected color range: dark yellowish green.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: granular, massive, or as rare tabular to equant crystals.

Often confused with

Arrojadite-(KFe) vs. its common look-alikes, and how to tell them apart in the field.

Often found alongside arrojadite-(kfe)

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

All properties

Chemical formula: (KNa)Fe(CaNa₂)Fe₁₃Al(PO₄)₁₁(PO₃OH)(OH)₂
Mohs hardness: ~5
Density: 3.527 g/cm³
Colors: Dark yellowish green
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Granular, massive, or as rare tabular to equant crystals
Cleavage: On {001}
Rarity: Rare
Uses: Collector
Host rock: A high-temperature (≈ 800°C) primary mineral in granite pegmatites

Where rockhounds find arrojadite-(kfe)

Classic worldwide localities

Smith mine, Newport, and the Palermo No. 1 and Nancy mines, North Groton, New Hampshire, USA
Nickel Plate mine, near Keystone, Pennington Co., South Dakota, USA (type locality)

Field-hunting tip

Where it forms: A high-temperature (≈ 800°C) primary mineral in granite pegmatites. If you start seeing graftonite, cassiterite, spodumene in float, you are in the right ground. Typical habit: granular, massive, or as rare tabular to equant crystals. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify arrojadite-(kfe)?+

Mohs hardness is ~5. Luster: vitreous. The streak is white. Common colors include dark yellowish green.

Where is arrojadite-(kfe) found?+

Notable localities include Smith mine, Newport, and the Palermo No. 1 and Nancy mines, North Groton, New Hampshire, USA; Nickel Plate mine, near Keystone, Pennington Co., South Dakota, USA (type locality).

What rocks look like arrojadite-(kfe)?+

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

What minerals are found with arrojadite-(kfe)?+

Arrojadite-(KFe) commonly co-occurs with Graftonite, Cassiterite, Spodumene, Beryl, Muscovite. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does arrojadite-(kfe) form in?+

Where it forms: A high-temperature (≈ 800°C) primary mineral in granite pegmatites. Working float back to the host body is the standard way to chase a fresh occurrence.

What is arrojadite-(kfe) used for?+

Arrojadite-(KFe) is used in collector.

Find arrojadite-(kfe) on the map

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