Galena

DZ 1368

DZ 1403

DZ 1317

DZ 1252

Flora

Galena (PbS). From the Greek Galena, meaning lead ore, galena is found almost exclusively in hydrothermal deposits where it forms rich accumulations, in remarkable paragenetic association with blende (ZnS), zinc ore. Galena is easily recognizable by its lead gray color, its metallic luster and its specific weight. It is one of the most important lead ores on which almost all world production is based. In Algeria, galena has been extracted for a very long time and the most important deposits are located in the north of the country, notably in El Abed, Boukaïd, Kherzet Youcef, Aïn Kahla. Calcite (CaCO3). Calcite or calcium carbonate is formed during a wide variety of geological processes and is one of the most common minerals in the earth's crust. Its varieties are quite easily recognized thanks to their large isolated rhombohedral crystals, their low hardness and the strong release of carbon dioxide when in contact with a drop of acid. Often colorless or milky white in color, calcite sometimes offers colored nuances because of the impurities it contains. Its uses, depending on the varieties and their properties, range from construction to optics, including the chemical industry. Feldspars. Feldspars are silicates of aluminum (Al), sodium (Na), potassium (K) or calcium (Ca) constituting the most important minerals in the composition of rocks. Due to their very numerous varieties, which are difficult to distinguish based on their morphological characters, their use remains extremely variable. Only potassium and sodium feldspars are of economic interest in glassware or ceramics. Conglomerate. It is a detrital sedimentary rock formed of pebbles (pudding) or angular fragments (breccias) of other rocks subsequently cemented.

30/04/2007

35 x 25 mm

Polychrome

Saliha Ammour

Bank of Algeria Printing House

14

Offset

5,00 DA

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300 000 exemplaires