Laurion - Minerals in Ancient SlagsLaurion


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Many tourists visiting Sounion's famous temple of Poseidon, some 45 miles to the southeast of Athens, while enjoying the fascinating sunset, do not realize that their gaze stretches over 'Laurion', an inland area larger than 200 square kilometres (125 square miles). In ancient times renowned for its silver production and then a major resource in Athens' prosperity.


At present the area is abandoned, although it remains a unique archaeological and mineralogical open-air museum. The jagged coastline with its typical Mediterranean flora has attracted an increasing number of tourists. In recent years the slag-heaps have disappeared to make way for forestation and residential construction.

Laurion is known among mineralogists for its exquisite macro and micro minerals. Tunnels and shafts dug to reach the layers of lead ore, containing 0.04 to 0.5 percent silver, created heaps of debris near the mine tunnels. This debris contains superb minerals of no interest to industrial exploitation. As mining took place here in antiquity as well as in the nineteenth and twentieth centuries it is possible, to this day, to find a large variety of tailing minerals with relative ease. This book surveys not these, but of a different group of Laurion minerals: the so-called slag minerals.

In ancient times furnaces were located both inland and along the coast. At the first stage of silver production the finely ground lead ore was heated with charcoal. The slags from these furnaces -containing residues of lead, silver and other minerals- were then piled in heaps. Many slag-heaps along the coast ended up in the sea. Here the effects of the sea-salt created a variety of new mineralizations in the slag cavities.

Lavrion's 2000-year-old slags gained worldwide renown in 1887 when R. Koechlin described laurionite as the first slag mineral in the 'Annalen des Naturhistorisches Hofmuseum Wien' (Annals of the Royal Museum for Natural History in Vienna).


The authors have studied slag minerals extensively since 1968.

Piet Gelaude has had many specimens determined by Pete Dunn (Washington) and several by Gunther Schnorrer (Gottingen), thus adding nealite, thorikosite and  mammothite to the list of slag minerals. Christian Rewitzer -in close cooperation with Rupert Hochleitner (München), Thomas Fehr (München), Günther Schnorrer, and Natale Perchiazzi (Pisa, Italy)- has determined a large number of slag minerals.

Rewitzer has recently discovered ludlockite, strontianite, shakovite and barstowite, among others. He has also written a detailed article on slag minerals in the Rivista Mineralogica Italiana.

Piet van Kalmthout photographed the best specimens of the three author's collections, has had some specimens determined by Rudy Swennen (Leuven) and coordinated the publication of
this book.


The 200 photographs with their accompanying descriptions have been selected to assist neophytes with eye-determination and to acquaint a broader public with the variety and beauty of these microscopic minerals. This book contains almost all known slag minerals of Laurion in their common crystalline form. Even the rare ones. Photos of some, as yet, undetermined slag minerals have been included. Needless to say the authors look forward to reader reposte in this.

Finally, this publication has a documentative function at this point in time, as new finds have been decreasing rapidly.

There is of late an increasing interest by environmentalists in the slag minerals. After all, the soil and the sea surrounding the Laurion area has been exposed to mining pollutants during a 5000 year period. The newly formed minerals of the slag-heaps, on land as well as in the sea, are also indicative of their burden to man and the environment.

Comments welcome!
Piet van Kalmthout