Many curious forms of life and their activities have been preserved in the rocks, some rare in occurrence and others common. In the seas as on land, animals with hard parts to their bodies, such as shells or skeletons, are more likely to be preserved than soft bodied animals like sea anemones or an octopus.
FOSSIL BIVALVES are common and occur worldwide and can be found in rocks of many ages. They are commonly employed to date rocks, as many extinct species lived only in certain time periods and any one finding a particular bivalve will know the rock it came from must belong to a certain time period. Such fossils are called index fossils.
On Vancouver Island, an example would be the extinct scallop called Monotis, which lived in Triassic times, some 200 million years ago. This thumbnail size pectin can be found in the Campbell River area. The soft parts of bivalves are rarely preserved, and perhaps rarest of all fossils associated with bivalves is the pearl.
The idea of a pearl being fossilized was first mentioned in an English publication in 169$, but it was not until early this century sufficient numbers had been found to form a collection for any museum and this was the British Museum of Natural History. Since then fossil pearls have been recorded twice from Canada.
The pearls are not gem quality pearls, but arc pearls nonetheless. The first was a discovery of two pearls from the common mussel. These were found near Cornwall in Ontario in 1956 when excavations for the Saint Lawrence Seaway were being carried out. The pearls date back to the Ice Age. A fossil pearl growth in the form of a large blister about half an inch long attached to the shell of a scallop was found in British Columbia in 1973.
This specimen is about 10,000 years old and was found in a gravel pit that has since been converted into John Diefenbaker Park at Point Roberts.
The oldest pearls found in Canada are undocumented and are in the University of British Columbia collections. These are two half pearls attached to an oyster shell. The oyster that made the pearls that are a shiny while color, lived more than 70 million years ago when a sea covered much of Alberta and Saskatchewan in the Cretaceous period. At that time and earlier lived a now-extinct bivalve called Inoceramus which died off about the time the dinosaurs ended.
There are fossils of about 50 different species to be found in Canada, some occurring north of Victoria to Texada Island. Although no fossil pearls from this oyster-like mollusc have been found in Canada, they have been found elsewhere, from England to the United States and have become known as the pearl oyster of the Cretaceous.
Four fossil pearls from an Inoceramus are in the Royal Ontario Museum and were originally found in Kansas. The largest of the four pearls is about a half inch across. The largest fossil pearl from an Inoceramus measures five inches. It is believed Inoceramus pearls were gem pearls, most of them if not all, have lost their pearly lustre and have become mineral stained over the course of millions of years.
Color in fossil pearls is usually lost, but there are cases where the color has survived. Near Redding, California, 10 pearls from an Inoceramus were found discolored with iron stains and near the mouth of the Columbia River a 10 to 55 million-year-old pearl was found in a fossil pearl oyster of Pteria. The color is described as being a pale brownish gray and shows a beautiful iridescent pearly lustre.
Shells can produce more than one pearl, in modern times, 1911 to be exact, a freshwater mussel from the Raisin River in Michigan was found containing no less-than 942 pearls, 100 being of marketable value! In the fossil record, a cluster of about 130 pearls was found adhered together on the Isle of Wight in 1926. These pearls are of Eocene age (40-56 million years ago).
THE MOTHER-OF-PEARL made by many types of shells can also survive if conditions are right. The mother-of-pearl from the coiled shells of ammonites which became, extinct about 70 million years ago, is often used as a semi-precious gemstone. Often when the mother-of-pearl fossilizes, the organic matter in it called conchiolin is replaced with minerals and the mother-of-pearl will turn an irridescent dark red and is prized for jewelry.
Fossil pearls when found are usually kept as museum pieces and are a rare prize for any collector.