Classic doublespar crystals from Helgustadir on a recent stamp
Source : Icelandic Post
Helgustadir is the name of a farmsite on the northern shore
of the Reydarfjord in the outer east of Iceland. This deposit of
outstanding transparent calcite was discovered in the 17th century and was
intermittently mined for many decades until 1924. The transparency of the
crystals where sufficient for the optical industry and therefore the calcite quickly
became famous as "Iceland spar" and its marvelous crystals were rapidly
distributed among the leading european scientists of that time. The initial
concepts of double refraction and crystal cleavage planes were first discovered
on calcite crystals from this site and led to a far better understanding
of crystal physics.
The calcite crystals, which are accompanied by small tufts of stilbite
crystals reach a size of several meters. RÖSLER (1981 : Lehrbuch der Mineralogie) quotes a maximum
size of 6 x 2 m , but dont give any more details. Other authors describe
7 x 7 x 2 m large crystals. A crystal of 230 kg is said to be on display
in the exhibition of the Museum of Natural History in London (yet unconfirmed).
Today there remain large dumps of the former mining activity, whereas
the mine as such is most of the year filled with snow and more or less inacessible.
It is still possible to find small cleavage pieces of double spar
calcite on the dumps, especially after periods of rain, which is not a
rarity in Iceland. However collecting is forbidden by law, as Helgustadir
was declared a national heritage site in 1975.
Update October 2006 : Courtesy of L. Kristjansson a detailed publication about the Helgustadir Iceland Spar locality is now available in the Library section.
Update January 2007 : An explanation table was added to the site recently, as can be seen at www.mindat.org, which also has some more images on the Helgustadir locality.
- More information about giant Iceland spar occurences can be found here (New Mexiko, USA), here (Hejiawan, China), and here (Garibaldi mine, Australia)
- Another remarkable Iceland spar deposit with crystals up to 0,7 x 0,5 cm occur in basalt from Nizhnyaya, Krasnoyarsk kray Siberia, GUS.
- Sharp yellow scalenohedral crystals up to 1 m occur with galena and sphalerite in the famous Tri State District, Oklahoma / Missouri / Kansas, USA.
- For more information about calcite pseudomorphs after giant ikaite crystals and crystal aggregates please look here and here.
- Large to giant crystals of calcite up to 1 x 1 m size from metamorphic marbles have been reported from Sterlingbush, New York, USA.
- Large dendritic ferruginous calcite crystals up to 2 m site are deposited by epithermal springs in Sisak Cermik, Turkey.
Snow filled Helgustadir mine site in April
Photo : Mr. L. Kristjansson
Inside the old quarry on a rainy day. Photo : Mr. L. Kristjansson
Slightly weathered calcite crystals from the Helgustadir mine
Photo : Flaviano, on www.flickr.com
Strange enough, scientific interest in the Helgustadir site
ceased almost completely in the 20th century. The most modern
literature survey about the Helgustadir site and its influence
on the scientific community was recently compiled by icelandic
Dr. Leo Kristjansson who works at the Geophysics Department
of Iceland university. It can be found here. Please have also a look at his website,
where you can find his extensive literature survey about Helgustadir
Mineralogy :
Calcite with minor zeolites
Crystal Size :
7 x 7 x 2 m confirmed
Geology & Origin :
Hydrothermal crevice filling in basaltic rock of tertiary age,possibly partly pneumatolytic
Status :
Often inaccessible due to snow conditions, dumps of former mining activity
Remarks :
A famous place of eminent importance to the history of natural sciences (see under "Resources")
Note the white remains of the calcite vein