Eudialyte

Eudialyte is a natural sodium-calcium zirconium silicate mineral of the trigonal eudialyte group, usually pink to deep red or brownish red. It forms in nepheline syenites and related pegmatites, and most gem material is massive rock from the Kola Peninsula, Russia, cut into cabochons, beads, spheres and carvings, often with black aegirine and white feldspar in the matrix. Transparent facetable crystals are rare and small.

Products made with this material

No products for this material yet.

Full material guide
Material facts

What the material is, where it comes from or how it is made, identification and care, from the cited sources.

Properties

Nature Natural mineral; no known treatments
Chemical formula Na4(Ca,Ce)2(Fe,Mn,Y)ZrSi8O22(OH,Cl)2 (approximate; composition varies)
Crystal system Trigonal; well-formed crystals very rare, usually massive
Mohs hardness 5–5.5
Specific gravity 2.74–3.00
Refractive index 1.591–1.633; birefringence 0.003–0.010
Color Pink, red, brownish red, yellowish brown, reddish orange
Luster Vitreous to greasy; may be dull
Radioactivity Mildly radioactive

Origins & sources

Eudialyte occurs in nepheline syenites, alkalic granites and their pegmatites. The Kola Peninsula (including the Khibiny massif, Russia) is the main source of material for cabochons and carvings. Small red facetable crystals come from Mont Saint-Hilaire and the Kipawa complex in Quebec, Canada; Greenland (for example Qaqortoq) yields crystals up to about 1 inch. Other sources include Magnet Cove (Arkansas, USA), Sweden, Brazil, Madagascar and Pilansberg (South Africa).

Identification

Eudialyte has a relatively low refractive index (1.591–1.633) with low birefringence, a specific gravity of about 2.74–3.00 and weak pleochroism. Massive material typically shows red eudialyte with black aegirine and white feldspar. Calcium-rich members called eucolite may be uniaxial negative with higher RI and SG. There are no known gem treatments, and synthetic eudialyte is made only for research.

Care

With hardness 5–5.5, eudialyte jewelry needs protective settings and occasional wear. It dissolves in acids, so clean it only with a soft brush, mild detergent and warm water. Pieces under 5 ct are considered safe to wear, but because it is mildly radioactive, store it enclosed and apart from other gems.

History & culture

History

The name comes from the Greek eu dialytos, "well dissolved" or "easy to dissolve", alluding to the mineral's easy solubility in acids.

Cultural meanings

Not collected yet

Traditional beliefs

Not collected yet

Sources

Collected Oct 23, 2026