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LOT 2525
Fossil Hammatoceras Ammonite
JURASSIC PERIOD, CIRCA 183-176 MILLION YEARS B.P.
6 1/4 in. (750 grams, 16.1 cm).
Large Hammatoceras insigne specimen showing the characteristic discoidal form with strong ribbing. [No Reserve]
ProvenanceFrom Toarcian Caluados, France.
From the private collection of Kenneth Machin (1936-2020), Buckinghamshire, UK; his collection of antiquities and natural history was formed since 1948; thence by descent.
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AUCTIONS:
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Brown Druzy Quartz Stalagmite Geode Display
Circa 140-120 million years B.P.Sold for (Inc. bp): £1,287
A polished underside of a geode containing upward-reaching stalagmites covered in druzy brown quartz and small, sparkling white quartz crystals; mounted on a custom-made display stand. 6 kg, 15 x 30 x 17cm, 20 cm including stand
From Artigas, Uruguay. Property of a London lady. -
Polished Fossil Coral Head Heart Group
Devonian Period, circa 417-354 million years B.P.Sold for (Inc. bp): £26
Comprising five heart-shaped specimens showing the internal structure of fossilised coral. 83.5 grams total, 24-35 mm
From a Cambridgeshire, UK, collection. -
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Large Iridescent Placenticeras Ammonite from Alberta
Bear Paw Formation, Upper Cretaceous Period, circa 76-73 million years B.P.Sold for (Inc. bp): £5,980
Placenticeras costatum with gem quality fossilised shell with some visible suture lines, conserved and stabilised with natural polish and acrylic lacquer, with excellent iridescence showing red, green, orange and gold colours. 952 grams, 26 cm
Found St Mary River Valley, Lethbridge Mining District, Alberta, Canada. Property of a Bristol, UK, gentleman collector. Accompanied by a certificate of authenticity, exportable under Moveable Cultural Property Permit no.7021-25-12-22-0102.
The striking iridescence of these ammonites from Alberta, Canada, termed 'ammolite', was given the status of a gemstone by CIBJO in 1981. An iridescent opal-like play of colour is shown in fine specimens, and is caused by the microstructure of aragonite, the same mineral contained in pearls and nacre. The thicker the structural layers, the more reds and greens are produced; the thinner the layers, the more blues and violets predominate. The ammonites are a group of molluscs that lived in the seas from the mid-Devonian (approximately 400 million years ago) to the end of the Cretaceous (65 million years ago). The sequence of events that famously killed off the dinosaurs also drove the ammonites to extinction.
