Genesis & Geology
140 million years ago, tropical conditions prevailed in northern Germany. The earliest age of the Cretaceous period, Berrias, saw the beginning of the genesis of Obernkirchener Sandstein®. The Bückeberg elevation is situated on the coastline of a Cretaceous sea that belongs to the prehistoric ocean of Tethys. From the southern mainland, powerful rivers flow into the sea and bring fine grains of sand that are deposited here. The coarser sand grains are deposited on the riverbeds further south due to their heavier weight. This natural filtration of Obernkirchener Sandstein® gives it its unique fine-grain and compact nature. Its structure is characterized by a smooth fine grain packed tightly with a gravel-like cement.
Pieces of evidence from the Cretaceous period were repeatedly covered in sand by storm surges over the course of time and solidified by diagenesis of the sandstone. These are often still discovered today - such as the typical wave surface from the bottom of a shallow body of water in our natural stone surfaces. Other traces of from this time can be found in the form of small fossil indentations such as shells, or the remains of grasses or wood, that all make each stone unique.
Obernkirchener Sandstein® has a dense, extremely fine and even granular structure. It is unstratified and homogeneous. Individual elements are hard to make out.
80% of the volume of Obernkirchener Sandstein® is made up of quartz crystals that are just 0.05mm in size. In addition, feldspar and mica can also be found in its composition. Occasionally, brownish yellow areas can be seen in the rock, which suggest the presence of iron (hydr)oxide. The main component is a dense, mostly xenomorphically formed quartz structure, that occasionally contains a conchoidal fracture. In addition, there is very fine and highly reflective light mica.
Obernkirchener Sandstein® shows very good resistance to freeze-thaw cycles. It is highly weathering-resistant and can therefore deal with today’s environmental impacts. Even after centuries, only minimal weathering can be observed on the Stiftskirche church in Obernkirchen (1153-1167).