Hauyne
Last updated: April 2026
Hauyne (also spelled Haüyne) is a rare blue feldspathoid of the sodalite group, found primarily in volcanic phonolite rocks. Gem-quality faceted hauyne is exceedingly rare and sought by collectors; most notable material comes from the Eifel volcanic region of Germany and from Vesuvius, Italy. Its vivid cornflower to royal blue color and extremely low RI (1.494–1.509) and SG (2.44–2.50) are the primary diagnostic characteristics — the RI is so low it falls below the range of a standard refractometer's scale, making it immediately distinguishable from all common blue gem simulants (sapphire 1.762–1.778, blue tourmaline 1.614–1.666, blue topaz 1.609–1.643).
Physical & Optical Properties
Key Differentiators
- Extremely low RI 1.494–1.509 — below refractometer scale upper limit; far below sapphire (1.762), tourmaline (1.614–1.666), and topaz (1.609–1.643)
- Very low SG 2.44–2.50 — noticeably lighter than sapphire (4.00), tourmaline (3.00–3.20), and topaz (3.49–3.57)
- Isotropic (cubic SR) — no birefringence, no dichroism; sapphire and tourmaline are both anisotropic
- Vivid cornflower to royal blue; often found as small crystals in volcanic matrix
- Exceedingly rare as a faceted gem; primarily a collector stone
Price Context
Price context is approximate. GemID is not an appraisal tool. Results are indicators, not certified valuations.
Measurement Guides
Identifying a hauyne? GemID walks through these tests in order — RI, SG, fluorescence, and more.
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