This is a short Rock crystal blade from Magdalenian deposits of the Gudenus cave 20 km north from Krems; Lower Austria (Legacy Dr. Bachmayer, former Director of the Vienna Natural History Museum).
Starting in 1881, Leopold Hacker, Ferdinand Brun and others started to explore the caves within the “Kremszwickel”, an area situated between the two source rivers of the Krems-river. They investigated important archaeological and paleontological cave sites, such as the Gudenus cave, Eichmayer cave and the Schusterlucke.
The material of the Gudenus cave was extraordinary rich and more than 1200 artifacts were recovered during these early excavations, which lasted until 1883. Unfortunately the Gudenus cave findings, that certainly belonged to different Paleolithic horizons, were mixed during and after excavation and finally published in a completely insufficiently manner in 1884.
In 1913 Josef Szombathy worked at the site, followed by Josef Bayer during the years from 1922 to 1924. The last sediments residues and artifacts were excavated in a rather clandestine manner by R. Bedarik, who exported the findings to Australia. He claimed that he had detected the remnants of different Middle Paleolithic levels, but the results of his operation were never published.
The only valid publication of the site remains that of Breuil and Obermaier in 1908, who tried to reconstruct the stratigraphy by a typological approach. They distinguished a Middle Paleolithic, later defined as a Micoquian ensemble by G. Bosinski, and a classic Magdalenian. The raw material, which was used, consisted of chert, quartz, flint, jasper and rock crystal. Many artifacts seemed to be produced directly at the site. The Magdalenian is characterized by backed bladelets, very fine and delicate bone needles and sagaies with incised longitudinal furrows for the insertion of microliths.
The Gudenus cave is the most important site of the Middle Paleolithic in Lower Austria and the only Austrian site with a Magdalenian.
Rock crystal is normally a poor choice for a knapping stone, as its crystalline structure is relatively course. Only large, pure crystals of rock crystal, can be used to produce longer blades, which are not present at the site. Why this material is preferred at Gudenus cave and several other sites remains an unresolved question.
In Europe Rock crystal was occasionally used during the Mousterian in S/W-France (Les Merveilles and Laussel in the Dordogne, La Chapelle-aux-Saints and Chez-Poure in the Corrèze). Rock crystal Solutrean leaf points are known from Le Placard (Charente), and from the rock shelter of Badegoule (Dordogne). Rock crystal was also used during the Hungarian Epigravettian and during the Magdalenian at Zitny Cave in Moravia.
Allmost everything about the Paleolithic in Lower Austria can be found here:
One page from Breuil and Obermaier 1908 showing rock crystal artifacts: