| People have always been fascinated by precious stones because of their lustre. But not only polished gems shine. Each raw mineral has, such as mica flakes in the river sand show, its very special characteristic luster. Gloss isn't simply measurable. It is usually described by comparison with objects ... morePeople have always been fascinated by precious stones because of their lustre. But not only polished gems shine. Each raw mineral has, such as mica flakes in the river sand show, its very special characteristic luster. Gloss isn't simply measurable. It is usually described by comparison with objects of everyday life ... (in german) |
| It is not possible to write a chapter about the mineral galena without looking at the history of lead and silver to name two of the most important raw materials and materials of humanity. How long people processed galena as main ore for the production of lead is unknown. As lead inter alia used as a ... moreIt is not possible to write a chapter about the mineral galena without looking at the history of lead and silver to name two of the most important raw materials and materials of humanity. How long people processed galena as main ore for the production of lead is unknown. As lead inter alia used as an additive to various melts (e.g. to bronze and the salt-cementation process for gold extraction) one can assume that the properties of this mineral were known before 3000 BC. Other sources speak of a history of lead about 7000-9000 years BC back. |