Ammolite from Placenticeras fossil ammonite, Alberta

Autor/Urheber:

James St. John

Attribution:

Das Bild ist mit 'Attribution Required' markiert, aber es wurden keine Informationen über die Attribution bereitgestellt. Vermutlich wurde bei Verwendung des MediaWiki-Templates für die CC-BY Lizenzen der Parameter für die Attribution weggelassen. Autoren und Urheber finden für die korrekte Verwendung der Templates hier ein Beispiel.

Shortlink:

https://dewiki.de/b/2c3d4a

Quelle:

Wikimedia Commons

Größe:

2248 x 1656 Pixel (2718937 Bytes)

Beschreibung:

Ammolite (5.5 cm across at its widest) - diagenetically altered, iridescent Placenticeras ammonite shell material (nacreous aragonite, CaCO3) from the Upper Cretaceous Bearpaw Formation of the St. Mary River Valley, Alberta, Canada.

---

Ammolite is biogenic gem material from Alberta, Canada. It has stunningly intense, iridescent rainbow colors. Ammolite is fossil shell material from Placenticeras ammonites. Ammonites are an extinct group of swimming squid-like organisms with planispirally coiled shells (the chambered nautilus in modern oceans is a distant relative of ammonites, but has a similar body plan). Ammonite shells were originally nacreous aragonite (“mother of pearl”) (CaCO3). Geologic studies have shown that ammolite gem material formed from slight diagenetic alteration of the original ammonite nacreous aragonite shell. Diagenesis has significantly intensified and brightened the play of colors.

Ammolite is mined, polished, and treated by resin- or epoxy-impregnation to stabilize it. Very rarely, complete specimens of Placenticeras ammonite shells preserved in ammolite are recovered - such specimens are exceedingly valuable (for example, see figure 2 of Mychaluk et al., 2001).

Name & classification: Placenticeras meeki or Placenticeras intercalare (Animalia, Mollusca, Cephalopoda, Ammonoidea, Ammonitina)

Stratigraphy & age: Bearpaw Formation, Campanian Stage, upper Upper Cretaceous, ~70-75 Ma.

Locality: mine in the St. Mary River Valley west or northwest of Welling and south-southwest of Lethbridge, southern Alberta, southwestern Canada.

---

Reference cited:

Mychaluk, K.A., A.A. Levinson & R.L. Hall. 2001. Ammolite: iridescent fossilized ammonite from southern Alberta, Canada. Gems & Gemology 37(1): 4-25.

Lizenz:

CC BY 2.0

Credit:

Ammolite from Placenticeras fossil ammonite (Bearpaw Formation, Upper Cretaceous, 70-75 Ma; mine in St. Mary River Valley, southern Alberta, southwestern Canada) 2

Bild teilen: