Introduction

Ethiopia is known to the world as the museum of Ethnography Archeology and Anthropology: for it is residence of footprint of civilization and the cradle of humankind. Therefore, the fame of the country goes far in calling the attention of the world intellectuals on various fields including Geoscientists.

Presently, mineral exploration activities are carried out through out the country. The Ethiopian geological Survey is the sole governmental organization vested the authority by law to meet the geo-science information requirement of the nation. In order to accomplish one of its tasks, the survey established a Geological Museum to procure, care, study and display different mineral, rock and fossil specimens for the use of the intellectual demand of the geoscientists, experts, visitors, and other interested groups.

Currently, the museum is engaged in introducing the geological history and mineral resources of the country, with its geological history and mineral resources to internal and external audiences The Geological Museum is building its capacity to play its role efficiently. The museum needs to make strong work relation with different countries’ geological museums and laboratories to enable an exchange of samples & share experiences. This in turn, will create means and ways to consolidate, upgrade and update the Geological museum.

To this effect, stamps are produced for selected samples of the museum in collaboration with the Ethiopian Postal Service. The stamps are distributed to various users including philatelists. In this fourth issue, the Geological Museum presents three industrial mineral samples quartz, gypsum, feldspar, and one dimension stone, Ambo sandstone.

Quartz (SiO₂)

Quartz is one of the common and abundant minerals on the earth crust; many varieties of quartz are used for making jewelry and different ornaments quartz are of different verities used for multi purposes. Agate and chalcedony are used in making scientific instruments, chemical and radio apparatus. Ground and crushed quartz are used in wood filler, ceramics, glass, polishing soap and as an abrasive. It is also used as a flux in metallurgical work and in making refractory bricks.

Quartz occurs widely in the Precambrian terrains in the form of veins and as component of pegmatites. Several quartz vein and quartz bearing pegmatite’s occur in Kenticha area in the Oromia National Regional State. With an estimated resource of 260,000 tons of good quality that can be used for glass and ceramics factories. Large quartz reefs are known in northern Ethiopia. However, the extent and quality of these occurrences are not yet known.

GYPSUM (CaSO₄.2H₂0)

Gypsum is calcium sulfate, naturally occur in close association with anhydrite (CaSO₄). Gypsum is used to retard the setting time of the cement (ave.3-6% added to clinker), as a fertilizer, as a source of Ca and S and a soil conditioner. Termed land plaster-gypsum is used as a fertilizer for specific crops like peanuts, legumes, potatoes, and cotton. It is also used as a substitute for sodium sulfate in glassmaking. Gypsum is inert with good absorbing capabilities (animal food extender; insecticide carrier). Together with inertness and lack of abrasiveness, some grades of gypsum are sufficiently pure to be used as a filter or diluents (paint, plastics, textiles, food, and pharmaceuticals).

Extensive gypsum and anhydrite resources are known from the Mugher (Sodoble) valley, the Abay beds, and from Jemma River, Ferfer, Dewalle, Adi Gudem and Hagere Selam. These occurrences are mainly associated with the Mesozoic sedimentary rocks and occur at many localities as intercalation with calcareous strata. The Adi Gudem and Hagere Selam gypsum has a resource potential of about 410,000 tons.

Gypsum also occurs as the upper most unit of the evaporitic sequence in the Danakil Depression, in association with Quaternary salt and potash deposits Patches of gypsum also occur in the lacustrine beds of the lower Awash River Valley near Asaita, in the Southern Afar region. A limited amount of gypsum is currently produced for domestic consumption mainly for the cement and stucco production of Mugher, Filikik near the Abay Bridge, Dewelle near Dire Dawa, Adi Gudem and Haare Selam near Mekele. The gypsum resources of central and northern Ethiopia have good potential for future development, due to their often-close proximity to large settlement areas.

Feldspars (X(AISi)₄O₈) where X is either and or K, Na, Ca)

Feldspars are alumino-silicates with varying amounts of K, Na and Ca in a solid solution series, the main commercial feldspar between the sodium (albite) and potash (microline) rich end members, and the sodium end of the sodium-calcium series (oligoclase).

In glass making feldspar is used as a source of Al₂O₃+Na₂O and or K₂0, and SiO₂ In ceramics, feldspar acts as a flux to form a glassy phase in bodies. In both glass and ceramics, feldspar contributes SiO₂. Feldspar is also used as filler in paint, plastics, and other industries.

Most feldspar in Ethiopia occurs in pegmatites and is K-feldspar. The resources of Kenticha and Bombase-Babile are relatively well explored. At Kenticha, 540 km south of Addis Ababa in the southern Adola Belt, pegmatite veins of good quality with a resource of some 500,000 tons of pure feldspar and an equal amount of quartz feldspar occur. Geological mapping has shown that there are abundant resources scattered throughout the area. The pegmatite dykes in the Bombas-Babile area are reported to contain 55% feldspar, with a total resource of about 52,550 tons.

Ambo Sandstone

Ambo sandstone is Triassic sandstone of the Adigrat group which is well known for its use as a construction material, cut and shaped into blocks or slabs for building (dimension stone) may be crushed for aggregate (construction). When sandstone, silica sand and quartzite are crushed or ground they are sources of SiO₂ and used for glass, ceramics, and chemical industries and are fluxing agents in iron and steel industries etc. The best potential of Ambo sandstone lies within the thick, red bed series of the Adigrat Sandstone along an axis from Ambo in the south, through the Abay Valley to Tigray in the north. Exploitation is mainly confined in the deposits near to the town of Ambo. Here, the cross-bedded, red and white sandstone is worked to ashlars, split bricks and slabs with the help of simple tools such as sledgehammers, wedges and crowbars. Products are distributed though out most of Ethiopia even though a major part of the production is used in the capital Addis Ababa.