What is a chert nodule?
What is a chert nodule?
Chert and flint nodules are often found in beds of limestone and chalk. They form from the redeposition of amorphous silica arising from the dissolution of siliceous spicules of sponges, or debris from radiolaria and the postdepositional replacement of either the enclosing limestone or chalk by this silica.
What is nodule in geography?
Nodule, rounded mineral concretion that is distinct from, and may be separated from, the formation in which it occurs. Nodules commonly are elongate with a knobby irregular surface; they usually are oriented parallel to the bedding.
What is a subterranean nodule?
Septarian or septarian nodules are concretions containing cracks and cavities that were filled in with minerals such as calcite (yellow) and aragonite (brown) causing the very unique patterns. These septarian nodules make for very interesting display pieces when cut and polished.
What is nodular limestone?
Nodules are rounded lumps of hard stone found within mudstones and limestones, which are often small but may reach metres in size. They are clearly distinct from the surrounding rock known as matrix.
How do I know if I have chert nodules?
Chert has four diagnostic features: the waxy luster, a conchoidal (shell-shaped) fracture of the silica mineral chalcedony that composes it, a hardness of seven on the Mohs scale, and a smooth (non-clastic) sedimentary texture. Many types of chert fit into this categorization.
How do you open nodules?
Some people use a rock hammer to open concretions. Although this method may crack it open quickly, it frequently causes the concretion to break in a way that does not expose the entire fossil. The best method to open concretions is to alternately freeze and thaw them.
What is the meaning of nodular?
: a small mass of rounded or irregular shape: such as. a : a small rounded lump of a mineral or mineral aggregate. b : a swelling on a leguminous root that contains symbiotic bacteria. c : a small abnormal knobby bodily protuberance (such as a tumorous growth or a calcification near an arthritic joint)
How is a nodule formed?
In general terms, nodules are formed as a result of infection of the roots by soil bacteria. The complex process by which plant roots are infected by rhizobia is known as infection. The complex process in which nodules are formed is known as nodulation.
How do you open a nodule?
Where is chert commonly found?
Chert is found in settings as diverse as hot spring deposits (siliceous sinter), banded iron formation (jaspilite), or alkaline lakes. However, most chert is found either as bedded chert or as nodular chert.
Is flint and chert the same thing?
Flint is gray to black and nearly opaque (translucent brown in thin splinters) because of included carbonaceous matter. Opaque, dull, whitish to pale-brown or gray specimens are simply called chert; the light colour and opacity are caused by abundant, extremely minute inclusions of water or air.
How do I get Ammonite nodules?
The better preserved ammonite fossils are contained in hard rounded nodules. Train your eyes to look for the dull grey muddy looking grey nodules, usually spherical or ovate in shape. They drop out of the cliffs and the sea tosses them about, wearing off the outer edges of matrix, exposing the ammonites within.
What kind of rock is a nodular chert?
…deposits exist—namely, bedded chert and nodular chert. Bedded cherts occur in individual bands or layers ranging in thickness from one to several centimetres or even tens of metres. They are intimately associated with volcanic rocks, commonly submarine volcanic flows as well as deep-water mudrocks.
Which is an example of a chert Arrowhead?
Chert Arrowhead: A chert (flint) arrowhead bound to a wooden arrow shaft with sinew. Image copyright iStockphoto / Brian Brockman. Chert cabochons: Occasionally, specimens of chert with attractive colors or interesting patterns are cut as gemstones. These chert cabochons are examples.
What kind of chert is found in Precambrian rock?
The banded iron formations of Precambrian age are composed of alternating layers of chert and iron oxides. It also occurs in diatomaceous deposits and is known as diatomaceous chert. Diatomaceous chert consists of beds and lenses of diatomite which were converted during diagenesis into dense, hard chert.
What’s the name for the red color of chert?
Abundant iron oxides in the chert can produce a red color. The name “jasper” is frequently used for these reddish cherts. Abundant organic material can produce gray or black chert. The name “flint” is often used in reference to the darker colors of chert.
What is a chert nodule? Chert and flint nodules are often found in beds of limestone and chalk. They form from the redeposition of amorphous silica arising from the dissolution of siliceous spicules of sponges, or debris from radiolaria and the postdepositional replacement of either the enclosing limestone or chalk by this silica. What is…