The "Jasper Mountain"
A further structur of subvolcanic origin in the Gilf Kebir crater-field (GKCF)

June 2010
Norbert Brügge, Germany
Dipl.-Geol.

With friendly permission by Richard de Nul, Belgium, which made all pictures available
Update: 19.12.2011 with new pictures by Ursula Steiner, Switzerland (below)

During an expedition to the Gilf Kebir in 2009 found Richard de Nul, and its companions, in the northern part of the Gilf Kebir crater-field (GKCF) a most remarkable subvolcanic structure. The crater-like mountain consisting of tilted sandstone layers with strongly siliceous and ferruginous impregnations. The visible rim of the crater is deeply silicified and rich in jaspers and chalcedony. They called the structure as "Jaspis (Jasper) Mountain". The location is about 24°N / 27°E  (the exact coordinates are known to me).

In the rare and small cavities of the massive jasper, chalcedony and Quartz crystals have been observed. Jasper (dense, opaque, microcrystalline) and chalcedony (fibrous cryptocrystalline) are both mineralogically a variety of quartz (SiO2). Jasper is usually red, brown or yellow coloured by oxides of iron. Due to the beautiful colours and the attractive banding these stones are often used as a decorative stone. In the past the prehistoric made tools of it. Fragments were found in the immediate vicinity of the hill.

The occurrence of Jasper is mainly bound on ranges of the silification in volcanic rocks or other penetrated rocks. On fissures circulate hot solutions during volcanic activities.

This is the first important occurrence of a significant amount of hydrovolcanic accumulated quartz in the Gilf Kebir crater-field (GKCF).
In relation to the origin is it not possible to recognize a relationship to the Libyan Desert Glass. The LDG was a highly enriched gel-like mass with low water content. Principaly, Jasper (Chalcedony) is a product of post-volcanic activities. The LDG is possibly a product of pre-volcanic activities.

Jasper has been positively identified by analysis of density and refractive index at the Academy for Mineralogy, Antwerp.

   

 

Surrounding of the Jasper Mountain

       
Quartz, Chalcedony, width: 3 mm                                                                                                  Jasper, width : 10 cm       

 
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