Mineral Guide · Mineral

Gadolinite-(Y)

Gadolinite-(Y) is a rare yttrium-bearing beryllium silicate, typically dark and associated with evolved pegmatites and alkaline rocks.

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Crystal structure

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Mineral properties

Formula: Y₂Fe++Be₂Si₂O₁₀
Class: Silicates
Crystal system: Monoclinic
Typical colours: black, brown, dark green
Lustre: Resinous, Vitreous
Hardness: 6.50-7.00
Specific gravity: 4.20-4.60
Crystal habit: Granular, Massive, Prismatic
Origin: rare-element pegmatites, alkaline complexes and metasomatised granitic rocks

Related varieties

Gadolinite-(Ce)

What is Gadolinite-(Y)?

Gadolinite-(Y) is a rare yttrium-bearing beryllium silicate, typically dark and associated with evolved pegmatites and alkaline rocks.

Mineralogy and structure

Reference formula: Y₂FeBe₂Si₂O₁₀. Gadolinite-(Y) is the yttrium-dominant member of the gadolinite group. Natural crystals may be altered and chemically zoned. Gadolinite-(Y) belongs to the silicates and has a monoclinic crystal system. Typical hardness is 6.5–7 on the Mohs scale and specific gravity is approximately 4.2–4.6.

Colour and appearance

Typical colours include black, dark green, brown. The usual prismatic, granular, massive habit and vitreous, resinous lustre are useful descriptive features, but colour alone is not diagnostic.

Formation and localities

Gadolinite-(Y) forms in or is associated with rare-element pegmatites, alkaline complexes and metasomatised granitic rocks. Important documented localities include Sweden, Norway, Russia, Madagascar, Canada and the United States.

Collecting and care

Display only and preserve the locality; avoid cutting or grinding unknown rare-earth-bearing material.

Sources and editorial review

Reviewed by NotOnlyRocks Editorial Team

Last reviewed: 31 August 2026

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