| In the late Middle Ages massive amount of Baryt which phosphoresced when it was gently heated, were discovered in Italy. This stone was named after its place of discovery "Pietra fosforica di Bologna" (phosphorescent Bologna stone) and was of great interest to alchemists. Although the name baryte ha ... moreIn the late Middle Ages massive amount of Baryt which phosphoresced when it was gently heated, were discovered in Italy. This stone was named after its place of discovery "Pietra fosforica di Bologna" (phosphorescent Bologna stone) and was of great interest to alchemists. Although the name baryte has been assigned centuries later, it may be assumed that the Bologna stone is the first description in the literature. A portrait about this famous mineral by Peter Seroka. |
| This report gives a lot of details of the history of this mine. Contribution from Michael Kommer (written in german language) ... moreThis report gives a lot of details of the history of this mine. Contribution from Michael Kommer (written in german language) |
| Aragonite is a calcium carbonate, chemically identical with calcite. The mineral calcite, however, differs from Aragonite due to its internal crystal structure. While the crystal system of calcite is trigonal, the system of aragonite is rhombic. Dense masses of small aragonite crystals are difficul ... moreAragonite is a calcium carbonate, chemically identical with calcite. The mineral calcite, however, differs from Aragonite due to its internal crystal structure. While the crystal system of calcite is trigonal, the system of aragonite is rhombic. Dense masses of small aragonite crystals are difficult to distinguish from calcite, but they are larger, they show a distinct habit. A lot of chapters in this portrait will give you much more details about this interesting mineral. Written and investigated by Peter Seroka. (Article in german) |
| Betrachtet man die Struktur von Kristallen, erkennt mam meistens verschiedene Arten von Symmetrien, wie Translationen, Spiegelungen oder Drehsymmetrien. Der Grund für das Auftreten dieser Symmetrien liegt darin, daß bestimmte Atomanordnungen in der Struktur besonders stabil sind; eine hohe Symmetrie ... moreBetrachtet man die Struktur von Kristallen, erkennt mam meistens verschiedene Arten von Symmetrien, wie Translationen, Spiegelungen oder Drehsymmetrien. Der Grund für das Auftreten dieser Symmetrien liegt darin, daß bestimmte Atomanordnungen in der Struktur besonders stabil sind; eine hohe Symmetrie erlaubt dann die ständige Wiederholung dieser besonders stabilen Konfigurationen in der Struktur. Die Beschäftigung mit der Symmetrie von Kristallen in der Kristallographie ist aus mehreren Gründen besonders wichtig - Ein Beitrag von Erik Hock |