EVERY KING MUST HAVE A FOOL OR RISK BECOMING A FOOL HIMSELF by Anne-Miek Bibbe
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Heterophrentis sp. - pyritized fossil rugose coral from the Devonian of Ohio, USA.
This is a fossil solitary rugose coral, commonly known as a "horn coral". Rugosans are an extinct group - they only occur in Paleozoic rocks. The soft parts were sea anemone-like creatures called polyps. The polyps made calcareous hard-part skeletons. Most rugosans were solitary, but some were colonial.
The coral's skeleton is now composed of pyrite ("fool's gold" - FeS2, iron sulfide), a preservation style referred to as replacement. The specimen comes from the Middle Devonian Silica Formation (also known as the Silica Shale) in northwestern Ohio. Pyritized fossils are relatively common in the unit - pyrite can replace hard parts or it can be a coarsely-crystalline coating atop calcareous shells.
The most common fossil replacement minerals are quartz, pyrite, and apatite. Quartz is SiO2 (silica) - fossils that have been quartz-replaced are said to be silicified (silicification). Many silicified fossils have rounded to pustulose structures covering their surfaces. These are called beekite rings, but they're composed of ordinary quartz. Replacement by apatite (calcium phosphate) is called phosphatization.
Other minerals have also been found replacing minerals - many are quite rare. Reported fossil replacement minerals include: anglesite, apatite, barite, calamine, calcite, cassiterite, celestite, cerargyrite, cerussite, chalcocite, cinnabar, copper, dolomite, fluorite, galena, garnet, glauconite, gumbelite, gypsum, hematite, kaolinite, limonite, magnesite, malachite, marcasite, margarite, opal, pyrite, romanechite/psilomelane, siderite, quartz, silver, smithsonite, specular hematite, sphalerite, sulfur, uranium minerals, and vivianite.
(List mostly from info. in Hartzell, 1906 and Klein & Hurlbut, 1985)
Classification: Animalia, Cnidaria, Anthozoa, Rugosa, Stauriida, Streptelasmatidae
Stratigraphy: Silica Formation, Givetian Stage, upper Middle Devonian
Locality: unrecorded / undisclosed quarry in the Sylvania area, far-northern Lucas County, northwestern Ohio, USA
Heterophrentis sp. - pyritized fossil rugose coral from the Devonian of Ohio, USA.
This is a fossil solitary rugose coral, commonly known as a "horn coral". Rugosans are an extinct group - they only occur in Paleozoic rocks. The soft parts were sea anemone-like creatures called polyps. The polyps made calcareous hard-part skeletons. Most rugosans were solitary, but some were colonial.
The coral's skeleton is now composed of pyrite ("fool's gold" - FeS2, iron sulfide), a preservation style referred to as replacement. The specimen comes from the Middle Devonian Silica Formation (also known as the Silica Shale) in northwestern Ohio. Pyritized fossils are relatively common in the unit - pyrite can replace hard parts or it can be a coarsely-crystalline coating atop calcareous shells.
The most common fossil replacement minerals are quartz, pyrite, and apatite. Quartz is SiO2 (silica) - fossils that have been quartz-replaced are said to be silicified (silicification). Many silicified fossils have rounded to pustulose structures covering their surfaces. These are called beekite rings, but they're composed of ordinary quartz. Replacement by apatite (calcium phosphate) is called phosphatization.
Other minerals have also been found replacing minerals - many are quite rare. Reported fossil replacement minerals include: anglesite, apatite, barite, calamine, calcite, cassiterite, celestite, cerargyrite, cerussite, chalcocite, cinnabar, copper, dolomite, fluorite, galena, garnet, glauconite, gumbelite, gypsum, hematite, kaolinite, limonite, magnesite, malachite, marcasite, margarite, opal, pyrite, romanechite/psilomelane, siderite, quartz, silver, smithsonite, specular hematite, sphalerite, sulfur, uranium minerals, and vivianite.
(List mostly from info. in Hartzell, 1906 and Klein & Hurlbut, 1985)
Classification: Animalia, Cnidaria, Anthozoa, Rugosa, Stauriida, Streptelasmatidae
Stratigraphy: Silica Formation, Givetian Stage, upper Middle Devonian
Locality: unrecorded / undisclosed quarry in the Sylvania area, far-northern Lucas County, northwestern Ohio, USA
I ain't no theologian, but I did not realize that the Easter Bunny was present at the resurrection.
A mineral is a naturally-occurring, solid, inorganic, crystalline substance having a fairly definite chemical composition and having fairly definite physical properties. At its simplest, a mineral is a naturally-occurring solid chemical. Currently, there are over 6100 named and described minerals - about 200 of them are common and about 20 of them are very common. Mineral classification is based on anion chemistry. Major categories of minerals are: elements, sulfides, oxides, halides, carbonates, sulfates, phosphates, and silicates.
The sulfide minerals contain one or more sulfide anions (S-2). The sulfides are usually considered together with the arsenide minerals, the sulfarsenide minerals, and the telluride minerals. Many sulfides are economically significant, as they occur commonly in ores. The metals that combine with S-2 are mainly Fe, Cu, Ni, Ag, etc. Most sulfides have a metallic luster, are moderately soft, and are noticeably heavy for their size. These minerals will not form in the presence of free oxygen. Under an oxygen-rich atmosphere, sulfide minerals tend to chemically weather to various oxide and hydroxide minerals.
The deep brassy gold masses in the specimen seen here are chalcopyrite, a copper iron sulfide mineral (CuFeS2). Many pyrite-like minerals exist, such as pyrite, marcasite, arsenopyrite, pyrrhotite, pentlandite, and chalcopyrite. Chalcopyrite has a metallic luster, a deep yellowish-brassy color, a dark gray streak, a hardness of about 3.5 to 4, and no cleavage. Many specimens have a multicolored iridescent tarnish, which can be artificially produced by exposure to certain chemicals - often acid. Chalcopyrite is an important copper ore mineral.
The other crystals here are siderite - iron carbonate, FeCO3.
Locality: unrecorded / undisclosed site in Guizhou Province, South China
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Photo gallery of chalcopyrite:
www.mindat.org/gallery.php?min=955
