The Gruszka Quarry is located in the town of Wojcieszów, on the western slope of the Bielec hill. Currently, it is a closed quarry with a length of 250 metres and wall heights up to 50 metres.
From this quarry, from the late 19th century until the 1970s, rocks conventionally referred to as “Wojcieszów limestones” were extracted. However, from the perspective of petrography (the study of rocks), they should be called marbles due to the metamorphic processes that caused changes in the structure and texture of the original limestones.
The Wojcieszów limestones are one of the most recognizable rocks in this region. Due to their resistance to erosion, they often form the summit parts of elevations in the topography. Examples of this can be found in locations such as Bielec, Połom, Miłek, and Osełka. The elevations in this area have a distinctive, latitudinal alignment. There are also isolated, dome-shaped hills such as Widok and Wapiennik. On all these hills, you can observe overgrowing former quarries from a considerable distance.
Two limestone varieties
In the Gruszka quarry, two varieties of Wojcieszów limestones predominate. The first of them is light or light gray. The rocks are massive, with thick beds only vaguely marked in some places. In geology, the term ‘bed’ is used when we can distinguish rock packages separated by surfaces at the top (roof) and bottom (sole) in a rock wall. In these rocks, one often observes so-called streaking, which is the result of the accumulation of iron and manganese compounds. The most intense streaking can be observed in the vicinity of the limestone with greenstones. Above, the frequency of occurrences of accumulations of iron and manganese compounds decreases.
The second variety consists of light gray and gray-brown, finely crystalline dolomites. These rocks are composed of the mineral of the same name – dolomite. n field conditions, dolomite can be distinguished from limestone using hydrochloric acid. Dolomite, unlike limestone, reacts with acid only after being powdered. A distinctive feature of this variety is fine lamination, characterized by the occurrence of millimetrr-thick layers within the bed.
Proofs of tectonic movements
In the quarry walls, numerous breccias of tectonic origin are also visible. These rocks form in places where faults occur, meaning where there has been a disruption in the continuity of layers and their displacement. Such movement causes the rock to break in the fault zone. Subsequently, rock fragments were reconnected with a binder originating, for example, from the precipitation of compounds from highly mineralized waters. A characteristic feature of tectonic breccia is that it is composed of numerous sharp-edged fragments of the rock located in the immediate vicinity.
Limestone weathering
Another geological process that is visible at first glance is the limestone weathering. Its result is the reddish-brown deposit found in numerous cracks, known as terra rossa. This type of weathering can occur in tropical climate conditions, which, in the case of Wojcieszów limestones, may have taken place during the Permian period.
Next to it is an old lime kiln, whose summit platform has been adapted to serve as an observation point.
