The salt mine in prehistoric times

In the compacted remains of the prehistoric Hallstatt mines archaeologists have discovered a large number of well-preserved items. This dense mixture of prehistoric waste rock and debris from salt mining is referred to as the “Heidengebirge”. Over many millennia it has been compacted by the pressure of the mountain to create an air-tight and salt-rich climate ideal for preserving organic material. As a result, finds from Hallstatt include dyed textiles, hand-worked leather, wooden tool handles, transport containers, wood chips, ropes, food remains, feces and even grass.

Scientific importance of organic finds from Hallstatt
The “Heidengebirge”
Differences in the “Heidengebirge” during the Bronze and Iron Ages
Preserved salt mining pits

Scientific importance of organic finds from Hallstatt

The material goods of prehistoric cultures were mainly composed of objects made from organic substances: primarily wood, but also other materials such as grass, bast, fur, leather, skin, wool, and flax. Organic materials survive for long periods only in very special conditions: underwater, or, in contrast, in extremely dry conditions, or in ice or salt, provided they are protected from animals, and from the sort of microbial activity that usually rapidly degrades organic matter. Archaeology usually deals with objects made of durable materials, such as stone, pottery, metal, bone or antler. Consequently, it typically only gives a partial picture of the past.

In the Hallstatt salt mine, the situation is entirely different. Everything discarded or lost there, over a period of thousands of years, has been preserved - even human excrement and food scraps. A wealth of remarkable organic finds has been preserved, from the stubs of old tapers, broken axe handles, fur caps, leather caps, leather shoes, scraps of cloth, animal skin and leather carrysacks, woven ropes and cords made of tree bast or plant fibre. All these things relate to the various stages of the prehistoric mining process, from mine-face extraction of salt in blacks with bronze picks to hoisting it out of the mine with thick ropes. Every find provides further insight into the living- and working environment of prehistoric miners. Nevertheless, there are gaps in the Hallstatt evidence: archaeologists only find those objects or fragments of objects that were lost or otherwise left in the prehistoric mineshafts. Only under exceptional circumstances do they find complete items of clothing, or unbroken tools; and there is evidence too that broken items were not simply discarded but recycled by being burnt in the mine.

The “Heidengebirge”

Thus the prehistoric objects that we find represent the residues of wider prehistoric mining processes: the stubs of lighting splints, parts of broken tools, excrement and boulders that were not worth removing. Such residue accumulated on the floor of the mine chambers and over time became totally absorbed into the salt matrix of the surrounding mountain. This is because the salt 'grows' as the high pressure of the surrounding rock pressing on the malleable salty clays of the Haselgebirge serves to fairly rapidly close any underground cavities not propped open. This malleability also affects the prehistoric galleries and mining chambers, which have hardly ever survived intact.

In fact, the ancient mining workings would not have been recognizable to miners of the historical period or to scholars had it not been for the artefactual remains of the prehistoric miners that came to light when sections were reopened. For many decades, archaeological excavations have focused on these layers or strata of ancient floor residues – the Heidengebirge – wherever it has been identified in the overall mining zone.

Differences in the “Heidengebirge” during the Bronze and Iron Ages

This work has now determined that the Bronze Age mine waste differs markedly from that of the Iron Age. The Bronze Age Heidengebirge consists of spent tapers and other discarded items, as well as clay and gypsum from mining activity. While salt was hardly ever left behind, in the Iron Age workings, large quantities of spoil was created from compacted spalls, chipped off when the larger chunks of rock salt were hacked out. Because the composition of this material is concentrated core-salt, the Iron Age Heidengebirge is also termed 'Core Heidengebirge'. While the Bronze Age miners removed the totality of mined salt, hoisting everything, including small chips and spalls to the surface for one use or another, the Iron Age miners focused exclusively on removing large platelike tablets of pure rock salt. The Bronze Age and the Iron Age also witnessed different techniques in action, judging by their different toolkits.

Preserved salt mining pits

In rare instances, the original voids above the mining waste have remained recognizable. This happened, where foreign material was washed in from above so that the natural closure process was hampered. The causes in such cases may be that a mine gallery was abandoned and filled up with water, which allowed sediments to wash in; more dramatically, natural disasters, such as major storms and landslips could at times wash in earth, rubble and even whole trees. The original form of the worked-out void can be reconstructed by removing such introduced surface material. We know of only one prehistoric void that survived without being filled with surface material.

In this case, the gallery was sealed off so completely that even air could not escape; the pressure of this air pocket exerted enough pressure to keep the void open. This void, known as the Chamber of Hearts (the Herzerlkammer in the gallery complex known as the Stügerwerk), has remained open for more than 2000 years. Here we are confronted with the absolutely unique circumstance of an unaltered Iron Age workface. The famous 'hearts' are in fact the negative forms left by the removal of the big plate-like chunks of rock salt.

(Reschreiter, H. – Kowarik, K. – Loew, C.)

Betriebsabfall (Heidengebirge) des bronzezeitlichen Salzabbaus, der fast nur aus abgebrannten Leuchtspänen und gebrochenem Werkzeug besteht. Salz wurde im bronzezeitlichen Bergwerk nicht zurückgelassen. (Foto: A. W. Rausch - NHM Wien)

Das Heidengebirge der Hallstattzeit besteht aus wieder verfestigtem Hauklein, das beim Schrämmen der "Salzherzen" anfiel. Es weist einen besonders hohen Anteil an reinem Steinsalz, dem sogenannten Kernsalz, auf und wird daher als "kerniges Heidengebirge" bezeichnet. (Foto: A. W. Rausch - NHM Wien)

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