| ... As already mentioned elsewhere, mining in Ilmenau dates back to the year 1200. In 1216, Count Poppo v. Henneberg was enfeoffed with the Bergregal by Friedrich den II. At that time one had discovered mineralised steep copper slate near Roda and on the Sturmheide. Presumably, individual miners had ... more... As already mentioned elsewhere, mining in Ilmenau dates back to the year 1200. In 1216, Count Poppo v. Henneberg was enfeoffed with the Bergregal by Friedrich den II. At that time one had discovered mineralised steep copper slate near Roda and on the Sturmheide. Presumably, individual miners had been enfeoffed, who extracted copper slate and sandstone in accordance with the mining freedom. This is generally regarded as the beginning of the first main period of Ilmenau mining. The ore was mined in small open pits to a maximum depth of 50m. ... A Contribution of {:10697:} |
| The term used in the plural "pyrites" has often been misused in the past or in common for marcasite, chalcopyrite, pyrrhotite and other yellow to brass-colored minerals. The word pyrite is derived from the Greek "pyrites lithos" (derived pyr = fire and lithos = stone) and describes a characteristic ... moreThe term used in the plural "pyrites" has often been misused in the past or in common for marcasite, chalcopyrite, pyrrhotite and other yellow to brass-colored minerals. The word pyrite is derived from the Greek "pyrites lithos" (derived pyr = fire and lithos = stone) and describes a characteristic of the mineral, when rubbing against steel or flint (flint) to generate sparks. In prehistoric tombs pyrite concretions and unrolled pyrite where found, which supposed to be used for lighting a fire. (Article in German) |
| Spinellsynthesen finden sich im Handel als komplette Schmelzbirnen, die ab und an einen annähernd quadratischen, aber abgerundeten Querschnitt besitzen. In der Nähe des Keimes finden sich selten abgerundete Oktaederflächen. Im Gegensatz dazu sind Korundbirnen in der Regel der Länge nach gespalten ... moreSpinellsynthesen finden sich im Handel als komplette Schmelzbirnen, die ab und an einen annähernd quadratischen, aber abgerundeten Querschnitt besitzen. In der Nähe des Keimes finden sich selten abgerundete Oktaederflächen. Im Gegensatz dazu sind Korundbirnen in der Regel der Länge nach gespalten, um die inneren Spannungen im Kristall zu lösen. Wird das Material durch Tempern von den Spannungen befreit, sind die Korundbirnen komplett und im Querschnitt rund oder eher abgerundet dreiseitig. Ein Beitrag von Klaus Schäfer |