The incredibly colourful photo of the week is a picture that I took at the Canadian Museum of Nature. It shows what has to be one of the most spectacular pieces of ammolite that I have ever seen. Ammolite is a bit of a mysterious substance and it is found in only a few places on Earth, notably in the Canadian Rockies.
Ammolite is actually considered a gemstone and it is one of the few official gems that has a biological origin. Ammolite, unsurprisingly, is found mostly on ammonites, which are extinct relatives of today’s squid and octopuses. It is actually formed of the original aragonite shell material. During the Cretaceous, when most of western North America was covered by a large tropical ocean the ammonites, and dinosaurs thrived in the area. The ammonites eventually died and their shells were covered by very fine clay/ash. Burial continued and this ash, which contained lots of iron, potassium and other metals, prevented the aragonite shells of the ammonites from altering to calcite, which is how most fossils are preserved. This is what gives ammolite the spectacular colours we see now.
Today ammolite is found only in a few units of the Bearpaw formation, which reaches from Alberta to Montana. This makes ammolite an extremely rare gemstone, albeit a somewhat fragile one, since it is quite soft. Despite the rarity of ammolite it is also relatively inexpensive. Indeed, a quick search on Ebay showed loads of pieces for under $10.