Mollusk Fossil - Mineral and Healing Properties
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- Mollusk Fossil
- Goniatite Fossil
- Mollusk Fossil
- Fish Fossil
Mollusks are an amazingly diverse group of animals that live in a wide variety of environments. They can be found inhabiting trees, gardens, freshwater ponds and streams, estuaries, tidal pools, beaches, the continental shelf, and the deep ocean. Some mollusks are excellent swimmers, others crawl or burrow in mud and sand. Others remain stationary by attaching themselves to rocks, other shells, or plants; or by boring into hard surfaces, such as wood or rocks.
Origin Of The Name
The words mollusc and mollusk are both derived from the French mollusque, which originated from the Latin molluscus, from mollis, soft. Molluscus was itself an adaptation of Aristotle "the soft things".
The mollusks are invertebrates and therefore lack a backbone; they are unsegmented and most exhibit bilateral symmetry. Most mollusks can be described as free-living, multicellular animals that possess a true heart, and that have a calcareous exterior skeleton that covers at least the back or upper surface of the body.
Adult mollusks can range in size from a few mm (0.1 in.) to over 22 m (>70 ft.) in length as documented for some giant deep-sea squids. Their weight can vary from a few mg (a fraction of an ounce) to over 227 kg (500 lb.) as recorded for the giant south Pacific Tridacna clams.
A striking feature of molluscs is the use of the same organ for multiple functions. For example: the heart and nephridia ("kidneys") are important parts of the reproductive system as well as the circulatory and excretory systems; in bivalves, the gills both "breathe" and produce a water current in the mantle cavity which is important for excretion and reproduction.
Where Is It Found
The pearly clusters are particularly common in association with galena, sphalerite, and calcite in low temperature veins from sites in Midwestern quarries of the USA. Especially in the Missouri, Kansas and Oklahoma lead district and areas like our specimens from the Meridian Quarry Black Rock, Lawerence County, Arkansas. Nice dolomite crystals are found in limestone pockets in the quarries at Rochester, New York. Large fine crystals have been found in Switzerland, in pegmatitic seams in North Carolina, and in veins in Colorado. Other locals include Ontario, Canada; Pamplona, Spain and Mexico.
What Do We Do With It
Every respectable rock collection contains a variety of these wonderful fossils.
The appearance and disappearance of species of fossils of any type at specific points in time can serve as age indicators for the rocks or sediments that contain them.
In addition to contributing relative age information about sedimentary deposits, mollusks provide the raw material for isotopic dating of Cenozoic lithologic units. The calcareous skeletons of mollusks contain the element Strontium (Sr). As they secrete their shells they absorb both isotopes of Sr (86Sr and 87Sr) from seawater and thus record the 87Sr/86Sr ratio present in seawater at that point in time. Measurement of this ratio allows scientists to determine an absolute numerical age for the deposit containing the mollusks' skeletons.
We can determine the environment or climate of ancient deposits by examining where and under what conditions the living relatives of the fossils exist. For example, today the snail genus Fasciolaria (Figure 5: D) is an extremely aggressive carnivore that lives in tropical and subtropical lagoonal or bay environments. When we find Fasciolaria in fossil deposits we can infer that the sediments or rock were formed in a tropical or sub-tropical shallow-water setting. In addition, by studying the worldwide distribution patterns of mollusks, inferences can be made about paleocean currents and paleoclimate on a global scale.
Invertebrate Fossils - Lesson 16 Part 2