Formel: (Na,K)3(Ca,Na)(Al3Si3O12)(SO4,S,Cl) = Feldspathoid
Colourless, greenishblue, blue
Hardness: 5,5-6
Density: 2,44-2,5
Refractive Index: 1,494-1,509
Crystal System: isometric


Hauyne is a rare mineral from the feldspatoid group.

Deposits of gem quality material exist exclusively in Afghanistan and the volcanic Eifel around Mending. However, the Afghan stones are far from the quality of the stones from the Eifel in terms of color.

The colors range from light blue to strongly saturated dark blue. The higher the sulfur content, the stronger the saturation. The lighter shades of blue show a yellow to orange fluorescence in the long-wave UV light. Unfortunately, clean gem quality stones are very rare and hard to find these days. With increasing size, the stones are usually very included and fractured and almost impossible to cut. Due to the rarity and the strong demand, especially in the Asian region, the prices are rising enormously. Stones in best quality are hardly to be found in sizes over 0,20 ct. Above 0,50 ct there are only a few specimens on the market and above 1 ct you usually do not find available. Prices of up to $20.000 per carat were reached in the past years for stones in best quality.

The deposits goes back to the eruption of the volcano about 11.000 years ago. Commercial mining of this gemstone never took place. The finds are exclusively due to collectors who find the Hauyne in the pumice in the pits around Mendig. Nowadays, however, access to these pits is forbidden for private persons, which is why there are hardly any finds worth mentioning.

The Hauyn has a rather low specific weight and therefore often appears larger than the carat weight would suggest.
Previously known more as a collector’s stone, it is increasingly being used in jewelry. The stone has a hardness of 5.5-6 on the Mohs scale, but should be handled with care due to its brittleness.

If you are interested, take a look at the Hauyne category.

For cut gems check here

For facet rough check here



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