Hauyne
Hauyne, also spelled haüyne, is a sodium calcium aluminum silicate sulfate belonging to the feldspathoid group, crystallizing in the cubic system. Its vivid blue color closely resembles lazurite, the mineral primarily responsible for lapis lazuli's color, though the two form in entirely different geologic settings. It typically occurs as small, well-formed dodecahedral crystals embedded in silica-poor volcanic rock.
Hauyne properties at a glance
| Type | Minerals |
|---|---|
| Chemical formula | (Na,Ca)4-8Al6Si6(O,S)24(SO4)1-2 |
| Mohs hardness | 5.5–6 |
| Crystal system | Isometric |
| Luster | Vitreous to greasy |
| Streak | Pale blue |
| Cleavage | Distinct dodecahedral |
| Fracture | Conchoidal to uneven |
| Specific gravity | 2.4–2.5 |
| Transparency | Transparent to translucent |
| Common colors | Blue, Sky blue, Greenish blue, White |
| Rarity | common |
Geology & background
Hauyne crystallizes directly from silica-undersaturated magmas, forming in volcanic rocks such as phonolite and leucitite where there is too little silica for quartz to form, allowing feldspathoid minerals like hauyne, nosean, and sodalite to develop instead. Classic localities include the Eifel volcanic district of Germany, where hauyne occurs in ejected volcanic blocks near Niedermendig, and Mount Vesuvius in Italy, both of which have supplied specimens to European collectors for well over a century. The mineral is named after French mineralogist René Just Haüy, considered a founder of modern crystallography.
Because hauyne crystals are usually small and embedded in dark volcanic rock, well-formed loose crystals are relatively scarce and prized disproportionately to their chemical simplicity. Collectors typically pay a premium for pieces where the blue grains are large enough to appreciate without a hand lens, since most volcanic matrix specimens show only scattered pinpoint crystals.
How to identify Hauyne
Hauyne appears as small, rounded to dodecahedral crystals, typically a rich cornflower to violet blue, though gray and colorless material also occurs, with a vitreous to slightly greasy luster and a pale blue streak. Hardness of 5.5 to 6 and a lack of the strong crystal faces typical of garnet, another dodecahedral mineral, help with identification, along with hauyne's much lower density. Its close resemblance to lazurite and sodalite means confirming hauyne often depends on its volcanic host rock and crystal form, since all three can share a similar blue color.
- Compare the specimen's color, luster, crystal habit, grain size, streak, and locality before confirming.
- Use multiple photos when possible, including a fresh surface and a close view of texture.
Where Hauyne is found
Reported from multiple localities worldwide; verify locality against specimen provenance when available.
How much is Hauyne worth?
| Entry-level specimen | $2 |
|---|---|
| Typical collector specimen | $20 |
| Premium specimen | $150+ |
Value depends on size, crystal quality, color, locality, rarity, damage, and provenance.
Common uses
- Collector specimens
- Education
- Field identification
- Industrial or lapidary use when suitable
Interesting facts
- Hauyne is named after Rene Just Hauy, an eighteenth-century French mineralogist regarded as a founder of crystallography.
- Its vivid blue color closely mimics lazurite, the mineral that gives lapis lazuli its color, despite forming in unrelated rock types.
- Fine hauyne crystals are typically found embedded in volcanic ejecta blocks rather than as loose, freestanding specimens.
Care & safety
Handle as a collector specimen until hardness, cleavage, and fracture are verified.
Avoid inhaling dust. Do not cut, grind, or polish unknown specimens without eye protection and a proper respirator.
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