Limburgite
As Limburgit a basanite is called ( a basaltic volcanic rock ) with glassy groundmass and porphyritic texture. The name derives from his Erstbeschreibungsort, the Limberg or Limburg in Sasbach am emperor chair in Baden- Württemberg from. Limburgit is not officially recognized rock name and is now used only for the deposits at the Kaiser chair.
Rock description
The Limburgit Sasbach consists of a reddish-brown or gray-brown glassy or microcrystalline groundmass, in which phenocrysts of olivine and clinopyroxene are. The olivine is more than 3 mm in size and usually results from only in weathered form, either as a yellowish limonite, or as red hematite. The clinopyroxene is black Ti - augite of up to 1 cm in size, which often has the characteristic octagonal cross sections, two head surfaces thanks to its euhedral growth. Twins and Mehrfachverwachsungen are often observed. In blowholes, which are very common in the rock, different minerals have after the rock formation by conversion processes formed, for example, zeolites ( faujasite, Philipsit and others), calcite, aragonite and opal ( Hyalite ). These secondary minerals make the Limburgit for mineral collectors interesting.
The locality at Limberg
At the northwest edge of the Emperor chair (I- VII) are open to several limburgitische lava flows formed in part as a block or Aa lava in seven quarries. They erupted during the late phase of the emperor chair development in the Miocene about 16 million years ago from a side crater of the volcano. The Limburgitströme together with an olivine - nephelinite lava flow as well as the remains of a cinder cone ( red wall in the quarry VII) the so-called Limberg Luetzel Mount complex. In the largest digestion, the quarry I, two Limburgitabfolgen are separated by a small powerful Tuffit and Seesedimentschicht.
Use
Due to the immediate vicinity of the Rhine Limburgitvorkommens the rock was broken in the 19th century in several quarries for building materials for straightening of the Rhine. Today, the Limburgit has no economic significance.