30 cm large glendonite crystals on display in the Moler Museet on Mors
Photo Source : Moler Museet Mors
Europe : Denmark : Glendonite (Calcite pseudomorphosing Ikaite) crystals up to
> 1 m size in the Moler deposits of Mors Island Coordinates :
56°56'N , 8°52'E : Hesselbjerg, Nyköbing, Mors Island, Denmark
Denmark ? This rather flat piece of land shall host gigantic crystals
? Yes, indeed and also some of the most interesting ! The Mors Island in northern Denmark host a major deposit of Moler
earth, which is an economically important mixture of clay and diatomite and is mined in huge open pits.
The tertiary Moler beds were tectonized by the advancing glaciers of the
last ice age and the once flatlying Moler sediment was intensely folded and overthrusted.
Some cliffs and open mine pits show spectacular folding which you never
would exspect in this part of the world. In the course of decade long Moler mining many small and some large "Molerkryds"
- Moler crosses - have been found. They consist of peculiar brownish calcite
crystals and may reach more than a meter length. The unusual form of the crystals,
which form stellate aggregates puzzled mineralogists for a long time. It was surely
calcite, but the crystal form remained a mystery for long and the odd crystals were,
together with similar ones from other localities, collectively named glendonites. Only recently it was learned, that glendonites are pseudomorphs of calcite
after ikaite. Ikaite, a hydrated form of calcite, forms as early stage calcium carbonate
precipitate in cold water environs. Sometimes as stellate crystal aggregates in
clay sediments and sometimes in spectacular large reef like formations as in
the Ikkafjord off the southwestern coast of Greenland (see separate Ikkajord entry on
this site).
Calcium carbonate precipitation in cold water is a fairly
new idea to the geoscience community and indeed may revolutionize the ideas of global carbonate
formation. Therefore the glendonites may hold important clues to the global
carbon cycle and long time climatic changes. So we have giant calcite pseudomorphs after giant ikaite crystals
here. But how do the giant ikaite crystals form in the moler sediment ?
This is still a mystery to be solved... The giant Moler crosses are on display in the very interesting Moler
Museum in Nyköbing, right beside an old moler pit with spectacular
glaciotectonic folding. Moler crosses are still found in the adjacent active mining area
from time to time, but access to the actively mined pits is generally restricted.
Update : March, 16th, 2005 :
The mystery mentioned above is solved, as is outlined on the Ikaite Homepage :
'Suess and his colleagues discovered large, amber coloured
crystals embedded in sediment cores recovered from the deep waters (1950 metres) of the
Bransfield Strait over the Antarctic shelf. Subsequent analysis identified the
mineral as ikaite which Suess and his co-workers believed to have formed in the sub-zero
bottom conditions from the interstitial solutions of organic-rich sediments undergoing
microbial decomposition.' Since this initial discovery more large in-situ ikaite crystals has been discovered in
other deep sea environs. Thereafter ikaite seems to be a quite common mineral, which
readily forms in calcium - oversaturated cold water, even in large and giant crystals.
- Massive amounts of glendonite crystal spheres occur at Olenitsa along the shoreline of the White Sea / southern Kola Peninsula, GUS.
- Very peculiar and sharp whitish glendonite / ikaite crystal aggregates up to several cm occur at Khatanga, Taimyr region, Sibiria, GUS.
- Information on the huge submarine ikaite towers in the Ikka - Fjord of western Greenland can be found here.
Large typical glendonite crystals up to 20 cm size are known from the Hunter Valley area, New South Wales, Australia.
True large ikaite crystals up to more than 1 m size have been recovered from the sea bottom in the Antarctic. These crystals quickly dissolve into calcite and water under surface conditions.
- Another notable ikaite occurence are the "thinolites" of the Mono Lake, California, which form huge "crystallized" tufa towers. These tufa towers are most likely a fossil example of the recent ikaite formations in the Ikka - Fjord mentioned above.
Heavily folded Moler sediment at Hanklit / Mors Island
Photo Source : unkown
2004 find of 1 m sized glendonite crystals in the Moclay pit
near Moler Museet, Mors Island
Photo Source : Moler Museet Mors
Glendonite specimen on display in the Moler Museet including
the famous giant 'Lynghojkrystallen' - the largest of its kind.
Source : Moler Museet Mors
Reconstruction of the once complete 'Lynghojkrystallen'
with the longest single 'arm' reaching 82 cm.
Photo source : Moler Museet Mors
The best source for information about the Moler industry and the glendonite
crystals is the danish Moler Museet at Hesselbjerg / Mors Island. Its certainly worth a visit, but unfortunately the museum website is down...
SUESS, E., BALZER, W. et al. :
Calcium Carbonate Hexahydrate from Organic-Rich Sediments of the Arctic Shelf: Precursors
of Glendonites. Science, 1216, 1128-1130.
More information can also be found on the Ikaite Homepage and on a recent article by GEIßLER (2005) in german language here.
Click below :
Mineralogy :
Glendonite (calcite after ikaite) pseudomorphs
Crystal Size :
stellate crystals up to > 1 m individual size. One of them known as the
'Lynghøjkrystallen' is the largest crystal ever found in Denmark
Geology & Formation :
In situ crystallisation in moler sediment = clay - diatomite mixture of tertiary age
Current status :
Museum, some of the abandoned pits can be visited, while access the actively mined area is restricted
Remarks :
Interesting example of early calciumcarbonate formation in sediments, which is probably a far more important
mechanism of carbonate precipitation than previously thought.
For more information on the mineral ikaite please look at www.mindat.org, Webmineral and the german Mineralienatlas.