Some educational notes on fossilized coral
Jul 23, 2014 5:21:58 GMT -5
Pat, snowmom, and 1 more like this
Post by jamesp on Jul 23, 2014 5:21:58 GMT -5
Time scale
From Florida Geological Survey:
Occurrence: Much of Florida’s agate, including the Tampa Bay agatized coral, formed in the Oligocene-Miocene Hawthorn Group sediments (see time scale). Once abundant at Ballast Point in Tampa, it is occasionally dredged up in the Tampa and Clearwater areas. It also occurs in limestones along the Econfina, Withlachoochee and Suwannee Rivers. An Oligocene variety is sometimes found in Suwannee Limestone quarries north of Tampa.
From Indonesianfossilcoral.com:
Geodes formed by partial replacement or casts of coral heads by low temperature chalcedonic or opaline silica are found in Florida. Florida has even declared fossil coral to be the “Florida State Rock”. The shapes and colors of these specimens from the Tampa Bay region, in north Florida and southern Georgia are unique. They are associated with Tertiary rock formations of 20 to 25 million years in age.
From Indonesianfossilcoral.com:
The process of silicification of Indonesian Miocene aged coral.
“Permineralization” is the process of filling pore space in and around the remnant hard coral skeleton with minerals deposited from solutions trapped or migrating thru the sedimentary pile as it is compressed into rock.
“Replacement” is the process whereby the original coral skeleton is replaced molecule by molecule with a mineral or minerals from a solution. For example, calcium carbonate (CaCO3) from the hard structure of the coral is replaced by silica (SiO2) from trapped or migrating solutions as rock was being formed.
This dual process preservation can occur with different accessory mineral concentrations and result in maintaining the contrast between the original soft tissues and the skeletal remains of the corals as different minerals impart different colors to the stone.
The geochemical and geological conditions under which these processes take place are typically slightly acidic, low temperature and low pressure. The resultant deposition of replacement product is a micro or crypto crystalline quartz commonly termed “agate”.
In Indonesia, entire coral heads are often completely preserved and appear just as they did 20 million years ago although their density is much changed by replacement and infill with silica, iron, manganese and other minerals. There are fern corals, brain corals, hex corals, honeycomb corals and many more.
Specimen coral heads are found in many stages of preservation. Some are mere casts with thin replacement of the outer skin and a pumaceous, leached or partial replacement of the inner core. Other coral heads are completely preserved by the dual process and can make beautiful polished slab specimens. The silica ranges from light weight amorphous opaline to dense cryptocrystalline chalcedony. Re-crystalization is often found on fractures resulting in fine glittering coatings of quartz druze. Rarely, entire specimens are coated in fine crystals. The fossilized coral heads come in all sizes and can weigh from 100grams to 100 kilograms.
Read more: www.indonesianfossilcoral.com/tech.html Slight mistake in article, figure 2 is figure 3, and figure 3 is figure 2
It would be a dream come true to set up camp in Indonesia and collect this stuff. Maybe with a polynesian gal if my wife would allow.
Many other agates occur in this territory. Maybe in a return life - the next go around, ha.
Other materials: indoagate.com
From Florida Geological Survey:
Occurrence: Much of Florida’s agate, including the Tampa Bay agatized coral, formed in the Oligocene-Miocene Hawthorn Group sediments (see time scale). Once abundant at Ballast Point in Tampa, it is occasionally dredged up in the Tampa and Clearwater areas. It also occurs in limestones along the Econfina, Withlachoochee and Suwannee Rivers. An Oligocene variety is sometimes found in Suwannee Limestone quarries north of Tampa.
From Indonesianfossilcoral.com:
Geodes formed by partial replacement or casts of coral heads by low temperature chalcedonic or opaline silica are found in Florida. Florida has even declared fossil coral to be the “Florida State Rock”. The shapes and colors of these specimens from the Tampa Bay region, in north Florida and southern Georgia are unique. They are associated with Tertiary rock formations of 20 to 25 million years in age.
From Indonesianfossilcoral.com:
The process of silicification of Indonesian Miocene aged coral.
“Permineralization” is the process of filling pore space in and around the remnant hard coral skeleton with minerals deposited from solutions trapped or migrating thru the sedimentary pile as it is compressed into rock.
“Replacement” is the process whereby the original coral skeleton is replaced molecule by molecule with a mineral or minerals from a solution. For example, calcium carbonate (CaCO3) from the hard structure of the coral is replaced by silica (SiO2) from trapped or migrating solutions as rock was being formed.
This dual process preservation can occur with different accessory mineral concentrations and result in maintaining the contrast between the original soft tissues and the skeletal remains of the corals as different minerals impart different colors to the stone.
The geochemical and geological conditions under which these processes take place are typically slightly acidic, low temperature and low pressure. The resultant deposition of replacement product is a micro or crypto crystalline quartz commonly termed “agate”.
In Indonesia, entire coral heads are often completely preserved and appear just as they did 20 million years ago although their density is much changed by replacement and infill with silica, iron, manganese and other minerals. There are fern corals, brain corals, hex corals, honeycomb corals and many more.
Specimen coral heads are found in many stages of preservation. Some are mere casts with thin replacement of the outer skin and a pumaceous, leached or partial replacement of the inner core. Other coral heads are completely preserved by the dual process and can make beautiful polished slab specimens. The silica ranges from light weight amorphous opaline to dense cryptocrystalline chalcedony. Re-crystalization is often found on fractures resulting in fine glittering coatings of quartz druze. Rarely, entire specimens are coated in fine crystals. The fossilized coral heads come in all sizes and can weigh from 100grams to 100 kilograms.
Read more: www.indonesianfossilcoral.com/tech.html Slight mistake in article, figure 2 is figure 3, and figure 3 is figure 2
It would be a dream come true to set up camp in Indonesia and collect this stuff. Maybe with a polynesian gal if my wife would allow.
Many other agates occur in this territory. Maybe in a return life - the next go around, ha.
Other materials: indoagate.com