limonite - teaching student specimens of limonite - UNIT OF 5 SPECIMENS

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Student specimens of  limonite - bog iron ore - Unit of 5 specimens.
Limonite was mined by George Washington's soldiers as a source of iron for cannon balls and bog iron was the primary source of Viking era iron. In bogs, limonite is concentrated by two processes. In the acidic environment of a bog, a chemical reaction forms insoluble iron compounds which precipitate out. A more important process involves the anaerobic bacteria
Gallionella
and
Leptothrix
. Growing under the surface of the bog, they concentrate iron as part of their life processes. These bacteria leave an iridescent oily film on the surface of the bog, called jambrák (iron slick) in Iceland.
Limonite also forms at the surface above veins of metallic ores where pyrite is common. The pyrite oxidizes, changing from iron sulfate to iron oxide and takes in water to become limonite. This imparts a yellow brown "iron hat" to these veins, a clue to prospectors that valuable minerals lie below.
As limonite gradually picks up water, it eventually converts to yellow ochre, a pigment favored by Native Americans. Initially brown and vitreous, limonite gradually takes on a mustard yellow tint. These specimens were collected from the iron hat above a vein.
Though limonite is brown, it gives a mustard yellow streak, an identifying characteristic.
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 want the "Oh, Wow!" effect when students see the set of specimens they are going to work with. 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.
You are purchasing a unit of five specimens.
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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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