Lecoqite-(Y) is an extremely rare yttrium carbonate mineral found in alkaline pegmatite environments. It typically occurs as small, pale yellow platy crystals or delicate radial aggregates within vugs of igneous rocks.

Hardness

3-4

Mohs

Luster

Vitreous

Streak

White

Transparency

Translucent

mineralrare

Lecoqite-(Y)

Hardness: 3-4
Luster: Vitreous
Streak: White
Transparency: Translucent

No image

Is this lecoqite-(y)?

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 lecoqite-(y) with a known reference. Lecoqite-(Y) sits at Mohs 3-4 — softer than the next harder reference, harder than the previous one.
2
Check the streak
Drag the specimen across an unglazed porcelain plate. Lecoqite-(Y) leaves a white streak.
3
Read the luster
Hold the specimen under a strong light. Lecoqite-(Y) typically shows a vitreous luster.
4
Match the color range
Compare against the expected color range: yellow, yellowish-white.
5
Look at form & habit
Crystal system: orthorhombic. Typical habit: platy crystals, radial aggregates.

Often confused with

Lecoqite-(Y) vs. its common look-alikes — and how to tell them apart in the field.

mineral

Dawsonite

Mohs 3

How to tell apart: Luster reads vitreous on Lecoqite-(Y) and pearly on Dawsonite.

How to tell apart: Luster reads vitreous on Lecoqite-(Y) and dull on Tengerite-(Y).

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Often found alongside lecoqite-(y)

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

All properties

Chemical formula: Na₃Y(CO₃)₃·6H₂O
Mohs hardness: 3-4
Density: 3.31 g/cm³
Colors: Yellow Yellowish-white
Streak: White
Luster: Vitreous
Transparency: Translucent
Crystal system: Orthorhombic
Crystal habit: Platy Crystals, Radial Aggregates
Cleavage: None
Rarity: Rare
Uses: Collector
Host rock: Alkaline Igneous Intrusions
Typical price: $50-300 per specimen

Where rockhounds find lecoqite-(y)

Classic worldwide localities

Mont Saint-Hilaire, Canada
Khibiny Massif, Russia

Field-hunting tip

Look in alkaline igneous intrusions country — that is the host setting where lecoqite-(y) typically forms. If you start seeing siderite, dawsonite, quartz in float, you are in the right ground. Field specimens usually show a platy crystals, radial aggregates habit, so train your eye for that shape before scanning the outcrop.

Common questions

How do you identify lecoqite-(y)?+

Mohs hardness is 3-4. It typically shows a vitreous luster. The streak is white. Common colors include yellow, yellowish-white.

Where is lecoqite-(y) found?+

Notable localities include Mont Saint-Hilaire, Canada; Khibiny Massif, Russia.

How much is lecoqite-(y) 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 lecoqite-(y)?+

Lecoqite-(Y) is most often confused with Dawsonite, Tengerite-(Y). A quick hardness test and a streak check separate the look-alikes faster than color alone.

What minerals are found with lecoqite-(y)?+

Lecoqite-(Y) commonly co-occurs with Siderite, Dawsonite, Quartz, Microcline, Aegirine. Spotting any of these in float or country rock is a useful trip signal.

What kind of rock does lecoqite-(y) form in?+

Lecoqite-(Y) typically forms in alkaline igneous intrusions. Working float back to the host body is the standard way to chase a fresh occurrence.

What is lecoqite-(y) used for?+

Lecoqite-(Y) is used in collector.

Find lecoqite-(y) on the map

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