Rare Earth Element Mineralization

 Rare earth element mineralization (REE) is found southeast of Lawdar in three contiguous, linear and veinlike bodies of carbonatites which croup out over an area of 2 km2.  Geological estimates of the carbonatite to a depth of 350 m, suggest the two largest bodies have reserves of 27.7 tons of rock grading 3.8% Tr2O3 and 14.5% Be (Abeulov, et al., 1981).  

Addition REE mineralization is found within the pegmatite rocks with estimated reserves of 100-120 thousand tons Tr2O3, 10,000 tons of Nb2O5 and 100-250,000 tons of Ba.  In the Nissab area the rare earth element mineralization occurs within the pegmatite rocks with reserve of 30-40,000 tons of Nb2O5 and 30-40,000 of Tr2O3 (Mkrtchan et al., 1977).  

Perlite & Pumice   

In Yemen Perlite is found as massive, columnar beds and dykes or sills associated with rhyolitic rocks & volcanic tuffs. These rocks are characterized by a vitrophyric structure with a compact-perlitic texture.  Pumice deposits in Yemen occur as thin beds within the volcanic ash beds or as a block mixed in with ash.  Extensive deposits of pale grey pumice and pumice occur on the plains east of Dhamar. The density of perlite after expansion varies between 21.3 - 34.9 pounds per cubic foot.  Resources total in excess of 335 million cubic meters of perlite and more than one billion cubic meters of pumice.

 

Gypsum and Anhydrite   

Gypsum deposits in Yemen occur within the Sab’atayn Formation (upper Jurassic), in the transitional beds of the (Upper Jurassic- lower Cretaceous), the Rus Formation (lower Eocene), the Libakhah, Ambakhah and Buwish Formation (Oligocene), and the Salif Formation (Middle-upper Miocene). Gypsum in Yemen is characterized by high purity and a range of colors. Chemical analyses of samples from deposits show them to contain 97.50% gypsum content (CaSO4, 2H2O). The resources of gypsum in Yemen are of more than 391 million tons.     

Rock Salt   

Rock salt in Yemen occurs as salt domes within the upper Jurassic Sab’atayn Formation (Amran Group) and within the Late Tertiary Salif Formation (Tehama Group).  The rock salt is associated with gypsum and anhydrite. Samples from selected deposits contained 98% NaCl.  Rock salt resources within Yemen total more than 365 million cubic meters. 

Scoria  

Scoria in Yemen occurs as volcanic cinders with basalt and ignimbrite rocks and on occasion with volcanic ash & clay materials.  Scoria in Yemen is characterized by dense vesicles in colors ranging from rusty red to black. Scoria is common within the Cenozoic volcanic. These could also be used to make Portland cement with Puzzolan.  Scoria resources total more than 613 million cubic meters.    

Pure Sandstone 

Pure sandstone in Yemen occurs within the Paleozoic (Wajid Formation) and Mesozoic (Kohlan Formation and Tawilah Group) as thick beds of consolidated to unconsolidated silica sand. These are characterized by high silica content (99.4% SiO2) with few impurities.  Quartz (98% SiO2) is widely distributed in pegmatitic rocks as pure quartz veins or lenses. Resources of silica sand exceed 160 billion cubic meters and quartz exceeds 13 billion cubic meters.  

Natural Zeolite 

Zeolite minerals in Yemen are commonly hosted by layers of volcanic tuff that are associated with volcanic glass, and in basic pyroclastic rocks that were emplaced during the Tertiary and Quaternary volcanism of  Yemen. Zeolitic rocks in Yemen are characterized by light colors (white, gray, green and yellowish) and fine-grained textures. Pumice and perlite fragments are often present. The types of natural zeolite in Yemen are clinoptilolite-heulandite, mordinite, stilbite, laumonotite, and natrolite, with percentage content varying from 14-85%. Chemical analysis of samples treated by magnetic separation indicates a potential increase of Na2O + K2O from 3.12 to 11.92% and a decrease of Fe2O3 from 11.2% to 1.76%.The resources of natural zeolite in Yemen are of more than 75 million cubic meters. 

Limestone and Dolomite   

Carbonate rocks (Limestone, Dolomite and Travertine) in Yemen are widespread and contained in sedimentary sequences ranging in age from Jurassic to Pleistocene.  They are distributed within five geological groups: Amran, Mahrah, Hadramawt, Shihr, and Tihamah.  Travertine occurs near natural hot springs, such as the Damt and Nihm areas.  Chemical analyses of limestone from several deposits reveal 60% CaO content with 95% whiteness, while chemical analyses of dolomite show it to contain 22.5% MgO.  The total resource of carbonate rocks is about 13.5 billon cubic meters.   

 Feldspar  

Feldspar in Yemen is found as small sized lenses in veins, nests, pegmatite rocks within granite rocks, granite gneiss rocks & in metamorphic schist. Feldspar in Yemen is characterized by white, grey, & pink colors. Its mineralogical composition is reported to be mainly potash feldspar and sodium feldspar. Chemical analyses of pegmatites rich in feldspar from some deposits show them to contain 22.5% Na2O with 22.33% K2O and 2.7 Fe2O3. The total resources of pegmatite rich in feldspar in Yemen is more than 23 million cubic meters.  

 Clay Minerals  

Clay minerals in Yemen occur within different geological periods.  Kaolinite with quartz in found in Sadah as beds lying on basement rocks (Precambrian) and is also a cementing material in sandstones of the Cretaceous Tawilah Group.  Shales and Marls occur in the Jurassic Akbara and Kohlan Formations and the Amran and Tawella Groups.  Extensive clay minerals (montmorillonite, attapulgite and sepiolite) occur in the Oligocene to Miocene Shihr Group.  Clay minerals also occur due to the weathering of volcanic rocks.  Loess and loam deposits (montmorillonite) of Quaternary age cover the plains.  The total clay mineral resource in Yemen is more than 120 million cubic meters.