Stronadelphite is a rare strontium-dominant member of the apatite group that typically forms as small, hexagonal prismatic crystals. It is primarily found in complex alkaline igneous environments and is highly valued by advanced collectors due to its rarity compared to common fluorapatite.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent

mineralrareApatite Group family

Stronadelphite

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

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Is this stronadelphite?

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 stronadelphite with a known reference. Stronadelphite 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. Stronadelphite leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Stronadelphite typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: colorless, white, gray.
5
Look at form & habit
Crystal system: hexagonal. Typical habit: prismatic crystals.

Often confused with

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

How to tell apart: Stronadelphite is noticeably harder (Mohs 5 vs. 3.5).

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Often found alongside stronadelphite

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

All properties

Chemical formula: Sr₅(PO₄)₃F
Mohs hardness: 5
Density: 3.5 g/cm³
Colors: Colorless White Gray
Streak: White
Luster: Vitreous
Transparency: Transparent
Crystal system: Hexagonal
Crystal habit: Prismatic Crystals
Cleavage: Indistinct
Rarity: Rare
Uses: Collector
Host rock: Alkaline Igneous Rocks
Typical price: $50-300 per specimen

Where rockhounds find stronadelphite

Classic worldwide localities

Kola Peninsula, Russia
Mount St. Hilaire, Canada

Field-hunting tip

Look in alkaline igneous rocks country — that is the host setting where stronadelphite typically forms. If you start seeing aegirine, microcline, nepheline in float, you are in the right ground. Field specimens usually show a prismatic crystals habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify stronadelphite?+

Mohs hardness is 5. It typically shows a vitreous luster. The streak is white. Common colors include colorless, white, gray.

Where is stronadelphite found?+

Notable localities include Kola Peninsula, Russia; Mount St. Hilaire, Canada.

How much is stronadelphite 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 stronadelphite?+

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

What minerals are found with stronadelphite?+

Stronadelphite commonly co-occurs with Aegirine, Microcline, Nepheline. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does stronadelphite form in?+

Stronadelphite typically forms in alkaline igneous rocks. Working float back to the host body is the standard way to chase a fresh occurrence.

What is stronadelphite used for?+

Stronadelphite is used in collector.

Find stronadelphite on the map

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