Geschichte: I have a holiday house at Mallorca's east coast, where I often climbed around as a child. There are a lot of interesting rocks around. It seems as if the island consists of Ca-bearing sediments and minerals like limestones. I once found a beautiful, translucent piece of calcite.
Geologie: This is a piece of calcite, which is the main constituent of limestone. However, this particular rock is no limestone. The calcite formed in a fracture: when rocks crack at shallow depths, hot water circulates through the fractures. The water contains dissolved minerals, like e. g. calcite. This calcite then gets exsolved, meaning it changes from the dissolved state to the solid state filling the fractures.