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Every serious opal enthusiast wants to have an opalized belemnite fossil in their opal collection. Belemnites are ancient Cephalopods from around 100 million years ago. Most opalized belemnites are found only in the South Australian opal fields around Cooper Pedy. Ancient cephalopods were squid like creatures that are related to the Octopus and Cuttlefish.
Belemnites are found in many countries including Sweden, England, Morocco and the USA. These creatures were prolific swimmers and vast quantities existed on earth but only Australian belemnites from Cooper Pedy are opalized. Beleminte fossils can be found in host rock all around the world. However in Australia the cavities left behind byu the Belemnite was filled with Opal instead of other material such as Quartz. This is why Australia is the only place in the world where Opalized Belemnites are found.
This make them a must have for opal enthusiasts. But they are very rare and to find one with full opal colour is very expensive. A torpedo shaped belemnite with translucent opals colours spectrum are extremely expensive. Most of the time they are found broken into pieces. Broken belemnites with clear or light sea blue colours are still reasonable priced.
Other ancient Cephalopoda include other molluscs such as
If you find a parcel of rough opal make sure you look for these. Octopus is extremely rare but there have been some findings in the past.
Belemnites were different to modern day squids as they had internal skeleton and no tentacles like modern squid. They had ten arms with studded hooks instead tentacles. In scientific community they are called Belemnitida (genus) belemnites, extinct cephalopods from Mesozoic to upper cretaceous era. Belemnoids were squids but more closely resembled the cuttlefish.
A 72 carat Black Crystal Opal belemnite fossil found in 2003. This opal is on display at Adelaide Museum celebrating 100 years of opal mining in the state. The exhibition is called simply OPALS.
Also on display is a six-meter Plesiosaurus that has an opalescent sheen in its skeleton.
South Australia was once under sea water in prehistoric times which was filled with marine creatures like aquatic reptiles. The director of the museum is excited to show opals that were formed when South Australia was under the sea and dinosaurs walked the planet. Compared to the famous opal mines at Lighting Ridge in New South Wales which were fresh water rivers and swamps so different prehistoric species are found in this area like mussel’s shells, pine cones etc.
The specimen pictured above is in the Seda Opals collection and consists of two belemnites a rare black crystal opal and a rare multi fire crystal opal.
When a belemnite died it would sink to the bottom of the sea and the sediment on the floor would be very muddy from the clay based soils. The decaying body would have been covered in this clay sediment very rapidly and stayed there for millions of years in desert type conditions.
After the sea eventually dried up the acidity in the sandstone soil greatly increased and the silica gel from the sandstone escaped and filled in crevices in the clay and in some areas these belemnites were encased in clay.
Over millions of years the acidic levels dropped and the silica gel hardened into opal in impressions of the decayed squid. This process was not common and most belemnites do not have opal colours. It is extremely rare to find multi colour opal or black crystal opal like the virgin rainbow.
It is understanding the rarity of this opal that makes one appreciate how rare and unique it is for mother nature to have produced such a spectacular belemnite opal
Opal pipes should not be confused with Belemnites. They are cylindrical shaped not torpedo shape and are found in many opal fields. They are formed in ironstone/sandstone potch.
These crystal pipes can be small only 1-2 mm wide or up to 12mm diameter and can be hollow or filled. These tubes are known as breccia pipes. Theory is that the hollow tubes had water running through them when formed and there is no relationship with prehistoric animals. Many opal pipes are cut into boulder crystal stones and sold with realizing that they were pipe opal.
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オパール愛好家なら誰でも、オパールコレクションにオパール化されたベレムナイト化石を持ちたいと考えています。ベレムナイトは、約1億年前の古代の頭足類です。ほとんどのオパール加工されたベレムナイトは、クーパーペディ周辺の南オーストラリアのオパール畑でのみ見つかります。古代の頭足類はタコとイカに関連する生き物のようなイカでした。
2003年に発見された72カラットのブラッククリスタルオパールベレムナイトの化石。このオパールは、アデレード博物館で展示されており、州での100年間のオパール採掘を祝います。展覧会は単にオパールと呼ばれます。
スケルトンに乳白色の光沢がある6メートルのプレシオサウルスも展示されています。
南オーストラリアは先史時代には海水の下にあり、水生爬虫類のような海洋生物でいっぱいでした。博物館の館長は、南オーストラリアが海の下にいて恐竜が惑星を歩いたときに形成されたオパールを見せることに興奮しています。ニューサウスウェールズ州のライティングリッジにある有名なオパール鉱山と比較すると、淡水川と沼地であったため、この地域ではイガイの貝殻、松ぼっくりなどのような先史時代の種が見つかります。
上に描かれた標本は、セダオパールコレクションにあり、珍しいブラッククリスタルオパールと珍しいマルチファイアクリスタルオパールの2つのベレンニットで構成されています。
ベレムナイトが死んだとき、それは海の底に沈み、床の堆積物は粘土ベースの土壌から非常に濁っていました。腐敗体はこの粘土堆積物で非常に急速に覆われ、砂漠タイプの条件で何百万年もそこにとどまっていたでしょう。
最終的に海が乾いた後、砂岩土壌の酸性度が大幅に増加し、砂岩からのシリカゲルが逃げて粘土の隙間に充満し、一部の地域ではこれらのベレムナイトは粘土で覆われました。
数百万年にわたって酸性レベルが低下し、腐ったイカの印象でシリカゲルが硬化してオパールになりました。このプロセスは一般的ではなく、ほとんどのベレンニットにはオパール色がありません。バージンレインボーのようなマルチカラーオパールまたはブラッククリスタルオパールを見つけることは非常にまれです。
このようなオパールの希少性を理解することは、母なる自然がこのような壮大なベレムナイトオパールを生み出したことがいかに希少でユニークなのかを理解させることです。
オパールのパイプをベレンニテと混同しないでください。それらは魚雷形ではなく円筒形であり、多くのオパール分野で見られます。それらは鉄岩/砂岩のポッチで形成されます。
これらのクリスタルパイプは、幅が1〜2 mmだけ、または直径が12 mmまで小さく、中空または充填することができます。これらのチューブは角recパイプとして知られています。理論では、中空管は形成されたときにそれらの中を水が流れ、先史時代の動物とは関係がないということです。多くのオパールパイプは、ボルダークリスタルの石にカットされ、パイプオパールであることを認識して販売されています。
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7人の人がこの記事が役に立ったと評価していますOpal fossils, including belemnites, have been recovered from Coober Peedy and another location, Mintabie, situated about 300 km from Coober Peedy. As of July 1, I 2019, the area will revert from government to aboriginal control, under the APY. Leases have not been renewed and the mines are expected to close.