Content

Opposite Heap

GPS: 49°49'20.579"N 17°42'55.199"E – map


A UNIQUE BRIDGE

A heap of an unusual shape. Extracted and processed slate roofing was transported from the mine to the village through the road leading to the settlement up on the Moraberg hill. This road had to be maintained, and therefore it was separated from the mine and the growing heap by the still existing high slate wall. The wall – before it partially slid down in the 1970s – was as high as 8.5 meters. The slate wall was so important that when in 1884 J. Nittmann sold the mine to Jakob Lintner, maintenance of the wall was established as an easement for the new owner. In the second half of the 19th century, mining here was on the rise, which also meant more and higher heaps of waste slate. So it happened that the southern part of the land where the mine is located could not take any more of the waste. The mine management therefore devised a remarkable and completely novel solution. They started to pile up heaps south of the road. First, waste slate was transported there with mining cars and dumped along the road. This created a narrow, about 150 m long heap. When this new heap was so high it was too difficult to dump any more slate on its top, another remarkable decision was made. They built a wooden bridge between the highest point of the supporting wall and the new heap. The bridge was at a height of about 12 m and allowed mining cars to dump more waste on the heap. At the top of the heap, cars could turn right or left, evenly distributing the waste slate on its both sides. The shape of this long, narrow, and high heap still documents the way it was created. Mining cars with waste slate accessed the heap thought a 1.5 m narrow gauge track running on both sides of the heap.


HEAPS

Existing data on slate mining in the medium complex near the Moravice river show that so far about 50 % of the entire deposit has been extracted to the surface. Almost a half has still remained in the mine in the form of rock fill and building materials.

Unlike in case of underground mining, surface mines extracted 100 % of the material. Interestingly, the raw material (slate) used for production of various traditional products formed usually only 10 – 12 % of the whole quantity of the extracted deposit. This is the reason why there are so many large heaps in the area. However, not all heaps are same, and therefore we classify them into several groups, of which we mention at least two basic ones.

 

HEAPS CAUSED BY SURFACE MINING – surface mining extracted all waste, including rock fill containing greywacke, sandstone, and conglomerate.

HEAPS CAUSED BY UNDERGROUND MINING – underground mining extracted only 50 % of the material and the rest remained in the mine, which was mostly low-quality raw material with a high content of rock fill. Therefore, underground mining did not contribute to heaps as much as surface mining. As a result, these heaps does not contain so much waste slate.

 

The foregoing is supported by a claim by J. Řihák:

"Naming them slate heaps is not entirely correct since it is known that all heaps located at the slate mines and quarries include not only waste slate but also more or less a waste of greywacke, sandstone, conglomerate, etc. It would be more appropriate to call them only heaps."

In the early days of mining roofing slate, what was dumped in heaps was not considered a raw material. As already mentioned, part of it was left in the mine and the rest dumped on heaps. Over time, however, especially with the advent of plastics in the early 20th century, even this material became a sought after commodity. First, it was crushed and subsequently milled into powder slate. Slate powder was added as a filler in various products. It found its application as an ingredient for the chemical and rubber industries, as a filler in the manufacture of bakelite, paints, varnishes, tires, high pressure plates, impregnating pastes, mastic asphalt screed on roads and runways, and even in some medicines. The gramophone industry also played a significant role in the processing of this waste. Micronized slate formed full 85 % of the mixture for the production of records. With minor modifications, this mixture was produced until 1965. A research of heaps carried out during the 20th century also resulted in a new lightweight construction material called expandit. It was made of crushed material of the sizes of 3 – 8, 8 – 15, and 15 – 25 mm by incineration in a rotary furnace at 1050 °C – 1150 °C. This was possible thanks to the specific properties of crushed slate from high quality heaps with a low content of waste rock. Ground slate was used as an ingredient for production of lightweight concrete and of the so-called porous slate concrete.

Also crushed slate of various grading found its application. It was used for production of slate concrete tiles, panels, lightweight shaped bricks, or various lightweight and construction mixtures. At present, it is still a very valuable raw material. Crushed slate of small grading is used in the manufacture of roofing felt. The coarser crushed slate – given its mechanical resistance after compaction – found a use in the construction of pavements. In the past, the local roofing slate was mined in zones 1 – 5 by digging mining pits directly in the second deposit zone. Slate was also mined by digging tunnels directly in the deposit zones. Therefore, it can be concluded that the local heaps are of very good quality with a minimum content of waste rock.

 

 

USE OF SLATE WASTE

Past

Crushed slate 3 – 25 mm

Grit 1 – 3 mm

Grit 0 – 3 mm

Powder 950 – 20,000 apertures / cm2

Expandit as the basic raw material for the production of lightweight slate concrete: panels, bricks, shaped bricks, beams, lintels, and other structural components

Ingredient in roofing felts
 

Production of roof tiles, wall tiles, kerbs
 

Production of porous slate foams, aerocrete, paints and varnishes, tyres, records, high pressure plates, school writing tools, and plastics
 

Present

Various kinds of large flat pieces

Grading 16 – 63 and more

Grading 4/8 and 8/16 mm

Grading 0/4 mm

Garden tiles and stones

Mulch slate

Gritting

Ingredient in roofing felts
 

 

Select language