chert - student specimens of light tan chert - UNIT OF 5 SPECIMENS

Description

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Tan chert - Student unit of 5 specimens. This chert is too soft for flint knapping, though a typical chert
This particular chert is tan or banded tan and brown and is from a deposit associated with magnesite, magnesium carbonate, a common association. Chert is a cryptocrystalline variety of quartz that will break with very sharp edges. For this reason it was sought after by stone-age tool makers. Flint is the related form that is found in chalk beds. These specimens were sharp-edged when collected. Any sharp edges have been rubbed against a geologist's hammer to remove the "edge," though the specimens appear untouched. This is a very typical chert, though not hard enough for flint knapping. It comes very close to glass in hardness, so will not scratch it easily, though we have a nice scratch from testing it on the back window of our VW van.
Chert can form in more than one way. Biochemical chert can form by solution and reprecipitation of the silica found in the shells of diatoms. This type of chert is a sedimentary rock. Chert can also form as a direct precipitation from hydrothermal fluids rich in silica. In this case it is often considered a cryptocrystalline variety of quartz like chalcedony and is thought of as a mineral. This chert was formed during hydrothermal alteration of lacustrine ash beds, with thge volcanic ash providfing the silica
If you are a science or earth science teacher purchasing this as a teaching specimen for your class, this should be compared with other varieties of quartz: agate, jasper, chalcedony and tiger eye, which are all microcrystalline or cryptocrystalline - showing no crystal structure.
You are buying a unit of five student specimens.
The photo is representative of what we ship.
We really don't like the tiny finger nail-sized specimens offered to students, as we feel these are too small to see rock textures and too small for examining the identifying characteristics of a mineral. We collect these specimens so that five specimens, or possibly six, will fit in a small flat rate box, and we keep the price low, as we know these will be used in a classroom. For teachers we count like a baker and a dozen is more than 12, since you will always need a few spares.
If you are a teacher, let us know.
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Shipping:
Ships in a small Priority Mail flat rate box unless combined with other purchases. We always combine shipping to get your purchase to you at the lowest cost. We do not charge for handling. We refund any overpayments on shipping beyond our actual cost. A second unit moves the shipment into a larger box. We can generally ship 4 to 5 student units or a number of hand specimens in that box with no further increase in postage.
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