New Amber Calcites from Norway
New Calcite find from Norway
One of the ‘new finds’ at the Munich show was the Amber Calcites from Norway. We were lucky to secure the majority of the specimens and are delighted to bring them to you on MinVision.
The Calcites were found in the Dalen-Kjørholt Mine, Kjørholt, Brevik, Porsgrunn, Telemark, which is a Limestone Mine in the Southwest Oslo region of Norway. This mine has long been an important mineral location in Norway, and over 250 Calcite morphologies have been noted there. The occurence of Calcite has been previously noticed at international shows for phantom crystals of Calcite (with micro crystals of Pyrite on the phantoms) and Calcite twins. Calcites from the mine are usually colourless, white or gray, but yellow and brown colours have occurred. The amber colours of this recent find are new to the mine.
The new find occured in mid 2007, with specimen extracted and brought to market by the end of Oct 2007. The Calcites were found in two pockets within the mine. They are all beautiful colour ranging from a firey amber to honey to pale brown. The crystals are generally translucent, becoming transparent, and with the rich amber colour, they look stunning with an internal glow when they are lit from behind. The luster of the specimens is excellent, ranging from bright through waxy, to a lovely satin or slightly frosted luster.
Within the two pockets, the discoverers believe there maybe up to 10 generations of Calcite growth. Of the specimens we received we were able to distinguish several generations, and certainly several forms of crystallization. Most are complex scalenohedral crystals, often with a younger generation of smaller scalenohedral crystals, but other specimens show a stalactitic/stalagmitic growth, often with a crystallized termination.
The earliest generation we can distinguish in our specimens is a massive Calcite matrix found on many of the specimens. The Calcite is translucent and relatively colourless or grey, forming cleaved rhombohedrons, or a breccia. On this Calcite is a coating of a thin layer of milky grey to greenish clay material (likely calcerous).
The specimens with the massive clay matrix, and clay coating, then have a generation of scalenohedral crystals. The scalenohedral crystals vary from very sharply formed, to more complexly crystallized, tending towards a ‘wheat sheaf’ appearance, with finely detailed growth patterns on the crystal faces. The rich amber coloured specimens tend to be the ones with the more complex growth, whilst the more honey-brown coloured exhibit sharper scalenohedrons.
Interestingly two of the sharply formed honey coloured specimens (BL531 , BL 513 ) show complex growth on several crystals where the scalenohedron splits into 3 triangular aligned terminations, a bit like a crown. This feature is also seen in the stalactitic/stalagmitic specimens. Perhaps these individual crystals have become stalagmitic?
Several of the specimens do not have scalenohedral crystals, but instead have what appears to be a stalactitic or stalagmitic growth. They have the same translucency, becoming more transparent, and wonderful rich colour; but have a smoother sculptural form like a stalactite, and a brighter luster.
They start with a narrow end, have smooth rounded growth and then become more crystallized ending in aligned terminations of a scalenohedral form. The terminations are aligned, often in clusters of three, and forming a triangular cross section, and the specimens look a bit arborescent.
One specimen (BL521) is definitely a stalactite, with a paddle-like shape, and a central thread or tube is visible running down the centre around which the specimen has formed.
Several later generations of Calcite are present.
One form is of small scalenohedrons, growing as single crystals or in rosette like clusters found on both the complex scalenohedrons, the sharp scalenohedrons and the stalacitic/stalagmitic specimens. This is likely to be several different generations, and range in size from <1mm to several mm.
A second form seen on the rich amber specimens with complex scalenohedrons is a later generation of sugary clusters of tiny sparkling crystals, grey due to the presence of clay, dotted over the amber Calcite.
These Amber Calcites are unique, for their unusual location – Calcite specimens are not common from Norway – , for their interesting crystallization and forms, and also for their beauty, - their complex growth highlighted by the satin luster, translucency and their rich amber colour, with takes on a fiery glow when back lit. They are aesthetic and display well, and are a worthwhile addition to any mineral collection.
Ref:
www.mindat.org
Hetherington, C.J. (2003): Calcite crystal growth at the Dalen-Kjørholt limestone mine, southwest Oslo Region. GAC-MAC-SEG Joint Meeting, Vancouver 2003, Abs. 84.
http://gac.esd.mun.ca/gac_2003/search_abs/sub_program.asp?sess=98&form=10&abs_no=84
Nordrum, F.S. (1993): Die Dalen-Kjørholt Kalksteingrube in Süd-Norwegen, ein neuer Fundort für exzellente Calcitstufen. MineralienWelt 4 (5), 49-56.
