Station: [2] Large expansion

Welcome to Steinkaulenberg, the only gemstone mine in Europe that is open to visitors. 

 The rock here, like the rock face of Idar-Oberstein, consists of volcanic rock that was formed two hundred eighty million years ago. 

At that time, there was enormous volcanic activity here in the Saar-Nahe region, with huge  amounts of lava accumulating up to eight hundred meters. 

 The lava flowed out of the upper mantle at a temperature of one thousand one hundred degrees Celsius. Countless small and big gas bubbles formed in the lava. Due to the unusually huge amounts of gas, the lava really foamed up. 

It then cooled down again and crystallized into solid rock. This process was already complete at one thousand degrees Celsius. The gas bubbles thus remained trapped under the already cooled lava. 

 As it cooled further, the gases trapped in the bubbles condensed into hot water containing carbon dioxide, which then permeated the rock. This released substances that could enter the cavities. Sulfates and acids, such as colorless silicic acid, were added, settled at the edge inside, and crystallized inward. 

 After millions of years, a geode was formed. 

If it is completely filled inside, it is called an almond. If a cavity remains, it is called a druse. 

Let's now take a look at the gemstones of the Steinkaulenberg: 

 We start with rock crystal. It is light, milky white, and most expensive when it is crystal clear. This is usually only the case in the crystal tips. Here you can clearly see the cavity in the middle, i.e., a druse. Next to it, we see another rock crystal, this time completely filled, i.e., an amethyst. 

 Here we see an amethyst druse, recognizable by its violet color. The different colors of the gemstones are caused by metal oxides. Iron dioxide is responsible for red to violet coloring, copper oxide for green, chromium aluminum for brown, and manganese for yellow. 

 There you can see two smoky quartz druses. Our gemstones here belong to the quartz group and are classified as having a hardness of seven. This is assessed according to the "Mohs scale of mineral hardness," a scale from one to ten. Chalk is soft and has a hardness of one, while diamond is very hard and has a hardness of ten. 

 Here we see jasper. We have it in a total of four colors: red, brown, yellow, and green. 

 The agates were particularly popular in our region, which is why this mine is also called the agate mine. Mainly the miners searched for agate almonds. If they were gray, they could be colored afterwards using a special process. 

 The miners at that time were mainly farmers from the surrounding area. They wanted to earn some extra income during the hard winter months. 

Gemstones have been found here since the mid-fifteenth century. 

At the beginning of the nineteenth century, people began to immigrate to South America in the hope of a better life, because times were very hard here. Unfortunately, they had to work as farmhands, for example, in order to survive. 

 By chance, former miners from Idar found a huge number of rare and beautiful agate almonds in Brazil, in Rio Grande, near the state of Rio Grande do Sul. 

These could be transported to Europe at low cost, and a trade developed. As a result, agate grinding experienced a real boom from eighteen hundred thirty four onwards. 

Gemstone mining in the Steinkaulenberg consequently declined and came to an complete end in nineteen hundred seventy. 

 Today, all the gemstones in the world are processed and sold here in the city.