Natural History - Amethyst Gem Tree

A large Diplomystus sp. fossil fish in a rectangular shale matrix. 2.8 kg, 52.5 x 28.5 cm



From Wyoming, Green River Formation, U.S.A. From an old Lincoln, UK, collection.

In southwest Wyoming (and parts of Colorado and Utah) in the Green River Formation are found some of the world's most outstanding specimens of fossil fish. The Green River system was composed of three lakes: Lake Ulinta, Lake Gosiute and Fossil Lake. These Eocene Lakes lay in a series of intermountain basins formed by geological events that uplifted the Rocky Mountains during the early Tertiary time. The climate was much different from the desert-like climate of this area today. Both the fauna (crocodiles, alligators, boa constrictors and some subtropical fish families) and the flora (such as large palm trees) indicate a climate much like that found along the Gulf Coast today. Large amounts of ash found in the sediments indicate that volcanoes were particularly active at this time.

A group of ten amethyst crystal specimens, each held in a white card collector's tray labelled 'Rio Grande do Sul, Brazil'. 587 grams total, 46-62 mm



From Rio Grande do Sul, Brazil. Mineral Imports, London, UK. Gregory, Bottley & Lloyd (Gregory's).

A pair of cut and polished natural coloured agate geode halves. 362 grams total, 86-90 mm



From Salto do Jucui, Rio Grande do Sul, Brazil. Private collection, Munster, Germany.