engleski

The morphology of calcite crystals in the Mežica mines

From over 500 samples 58 calcite crystals from Mežica mines were selected and their habitus, crystal forms and the crystal type determined. We identified 59 different forms and coordinated their indices with the parameters of the unit cell. Five main types of calcite crystals were distinguished: 1st type: scalenohedral crystals with the dominant crystal form {;214};, 2nd type: rhombohedral crystals with the dominant crystal form {;104};, 3rd type: rhombohedral crystals with the dominant crystal form {;018};, 4th type: prismatic crystals with the dominant crystal forms {;100}; and {;018};, and 5th type: rhombohedral to scalenohedral crystals with acute negative rhombohedrons and scalenohedrons as the dominant crystal forms. Two additional types of crystals were distinguished. The first one comprises barrel-like crystals without any dominant crystal forms and crystals with faces formed by dissolution of crystals. Of the twins the most frequent occur those with the twinning planes (018) and (001), while twins with the (012) twinning plane are the rarest. The morphology of crystals was linked to their place of nucleation in the Mežica mines, and some of the characteristics of calcite crystal described with respect to their position in the mines and to the parageneses in which they appear. According to the morphology also the succession of crystalization of calcite crystals was determined.

calcite; crystal morphology; twins; crystalization succession; Mežica Mines

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