Fengchengite is a rare sodium calcium iron silicate, typically rose to deep rose. It was approved as a distinct mineral species in 2007. It was first described from near Saima Town, ~60 km NNE of Fengcheng City, Liaoning Province, China.

Hardness

Mohs

Luster

Vitreous

Streak

White

Transparency

Transparent to translucent

mineralrareGarnet Group family

Fengchengite

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

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Is this fengchengite?

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 fengchengite with a known reference. Fengchengite 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: rose, deep rose.
5
Look at form & habit
Crystal system: trigonal.

Often confused with

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

mineral

Almandine

Mohs 7-7.5

How to tell apart: Almandine is the harder of the two (Mohs 7-7.5 vs. ~5).

How to tell apart: Spessartine is the harder of the two (Mohs 7-7.5 vs. ~5).

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Often found alongside fengchengite

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

All properties

Chemical formula: Na₁₂☐₃Ca₆Fe³⁺₃Zr₃Si(Si₂₅O₇₃)(H₂O)₃(OH)₂
Mohs hardness: ~5
Density: 2.90 g/cm³
Colors: RoseDeep rose
Streak: White
Luster: Vitreous
Transparency: Transparent to translucent
Crystal system: Trigonal
Cleavage: None
Rarity: Rare
Uses: Collector, Scientific research
Host rock: In agpaitic nepheline syenite and pegmatite, crystallized directly from a REE-, U-, Th-, and Zr-rich alkaline magma enriched in volatile components

Where rockhounds find fengchengite

Classic worldwide localities

Fengcheng, Liaoning Province, China

Field-hunting tip

Where it forms: In agpaitic nepheline syenite and pegmatite, crystallized directly from a REE-, U-, Th-, and Zr-rich alkaline magma enriched in volatile components. If you start seeing microcline, orthoclase, albite in float, you are in the right ground.

Common questions

How do you identify fengchengite?+

Mohs hardness is ~5. Luster: vitreous. The streak is white. Common colors include rose, deep rose.

Where is fengchengite found?+

Notable localities include Fengcheng, Liaoning Province, China.

What rocks look like fengchengite?+

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

What minerals are found with fengchengite?+

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

What kind of rock does fengchengite form in?+

Where it forms: In agpaitic nepheline syenite and pegmatite, crystallized directly from a REE-, U-, Th-, and Zr-rich alkaline magma enriched in volatile components. Working float back to the host body is the standard way to chase a fresh occurrence.

What is fengchengite used for?+

Fengchengite is used in collector, scientific research.

Find fengchengite on the map

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