Ammonite crystal8/4/2023 Often confused with Opal the colour & effect is caused primarily by Aragonite with varying micro impurities such as Pyrite & silica. It is classified as a biogenic gemstone along with Amber & Pearl. Ammonites from the Gandaki river in Nepal are called shaligrams, Hindus believe these to be a manifestation of the God Vishnu.Īmmolite is a term that refers to a jewellery quality gemstone material found on the outer shell of some Ammonites from specific regions such as Canada & Madagascar. They were considered to be evidence of divine action & were hailed for their perceived healing or divination powers. In medieval Europe, they were thought to be petrified snakes & referred to as "snakestones" or "serpentstones". Historically Ammonites have played a significant role in science, religion, economy & general human evolution. Females are often found to be larger then males this is theorised to be an evolutionary requirement of logistics, being females needed room for eggs & therefore became larger then their male counterparts. Control was achieved by using a siphuncle (tube like structure) to fill or release varying amounts of different solutions such as gas, air or water within the chambers. ![]() The smaller earlier segments were internally closed off into sectioned chambers which the animal would use to manipulate & maintained its buoyancy & therefore swim. As Ammonites grew they continually added incrementally larger chambers of Aragonite to the coil at the open end. Generally Ammonites formed in spiral like structures however a few species of heteromorphs took helically spiraled & non spiraled forms. These sea dwellers had an internal soft body which occupied the largest segments of the shell at the end of the coil this section is called the body chamber. They help date rock & other fossils that may accompany them in the strata layer. Ammonites have proved to be excellent index fossils due to their wide distribution & rapid continual evolution. Due to the presence of these crystalline structures fossilised specimens can display stunning crystals of Calcite & Aragonite within the chambers. ![]() ![]() They then secrete ions to activate the formation of calcium carbonate crystals & tailor the environment with pressure or other means to form Aragonite instead of Calcite. Known as the horned God he was historically depicted adorned with ram’s horns upon his head.Īn Ammonites shell is essentially crystal, it grew this by secreting a specialised protein called conchiolin which provides the structure to nucleate the crystals. Incited by their spiral shape the name Ammonite is a derivative of ammonis cornua meaning horns of Ammon an ancient reference to the Egyptian God Amun-Ra / Ammon. The name Cephalopoda / Cephalopod comes from the Greek ‘kephale’ meaning head & ‘podia’ meaning foot an anatomical reference to the head region tentacles. They then became extinct during the Cretaceous-Paleogene mass extinction event. Ammonites dominated many marine environments for an extensive period of around 300 million years from the late Silurian to around 65 million years ago at the end of the Cretaceous period. They where predatory animals with sharp beaklike jaws called aptychi that where surrounded by tentacles used to snare prey. Ammonoids generally referred to as Ammonites are an extinct marine mollusc belonging to the Cephalopoda class of fossils.
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