Arrojadite-(KNa) is a complex phosphate mineral typically found as massive or granular aggregates within phosphate-rich granite pegmatites. It is often identified by its characteristic greenish-brown color and its association with other primary and secondary phosphate minerals.

Hardness

3.5-4

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrareArrojadite Group family

Arrojadite-(KNa)

Hardness: 3.5-4
Luster: Vitreous
Streak: White
Transparency: Transparent

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Is this arrojadite-(kna)?

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-(kna) with a known reference. Arrojadite-(KNa) sits at Mohs 3.5-4, 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: yellow.
5
Look at form & habit
Crystal system: monoclinic. Typical habit: massive, granular, or anhedral grains.

Often confused with

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

mineral

Triplite

Mohs 5-5.5

How to tell apart: Triplite is the harder of the two (Mohs 5-5.5 vs. 3.5-4).

Compare →

Often found alongside arrojadite-(kna)

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

All properties

Chemical formula: KNa₃(CaNa₂)Fe₁₃Al(PO₄)₁₁(PO₃OH)(OH)₂
Mohs hardness: 3.5-4
Density: 2.84 g/cm³
Colors: Yellow
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Monoclinic
Crystal habit: Massive, granular, or anhedral grains
Cleavage: On {001}
Rarity: Rare
Uses: Collector
Host rock: Along veins in sandstone formed during very low-grade metamorphism

Where rockhounds find arrojadite-(kna)

Classic worldwide localities

Yukon Territory, Canada (type locality) and the Victory Mine, South Dakota, USA
Mount Wills pegmatite field, Victoria, Australia

Field-hunting tip

Where it forms: Along veins in sandstone formed during very low-grade metamorphism. If you start seeing lazulite, hematite, fluorapatite in float, you are in the right ground. Typical habit: massive, granular, or anhedral grains. Train your eye for that shape before scanning the outcrop.

Common questions

How do you identify arrojadite-(kna)?+

Mohs hardness is 3.5-4. Luster: vitreous. The streak is white. Common colors include yellow.

Where is arrojadite-(kna) found?+

Notable localities include Yukon Territory, Canada (type locality) and the Victory Mine, South Dakota, USA; Mount Wills pegmatite field, Victoria, Australia.

What rocks look like arrojadite-(kna)?+

Arrojadite-(KNa) 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-(kna)?+

Arrojadite-(KNa) commonly co-occurs with Lazulite, Hematite, Fluorapatite, Quartz. Spotting any of these in float or country rock is a useful trip signal.

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

Where it forms: Along veins in sandstone formed during very low-grade metamorphism. Working float back to the host body is the standard way to chase a fresh occurrence.

What is arrojadite-(kna) used for?+

Arrojadite-(KNa) is used in collector.

Find arrojadite-(kna) on the map

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