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Cerium was originally isolated in the form of its oxide, which was named ceria, a term that is still used. The metal itself was too electropositive to be isolated by then-current smelting technology, a characteristic of rare-earth metals in general. After the development of electrochemistry by Humphry Davy five years later, the earths soon yielded the metals they contained. Ceria, as isolated in 1803, contained all of the lanthanides present in the cerite ore from Bastns, Sweden, and thus only contained about 45% of what is now known to be pure ceria. It was not until Carl Gustaf Mosander succeeded in removing lanthana and "didymia" in the late 1830s that ceria was obtained pure. Wilhelm Hisinger was a wealthy mine-owner and amateur scientist, and sponsor of Berzelius. He owned and controlled the mine at Bastns, and had been trying for years to find out the composition of the abundant heavy gangue rock (the "Tungsten of Bastns", which despite its name contained no tungsten), now known as cerite, that he had in his mine.[34] Mosander and his family lived for many years in the same house as Berzelius, and Mosander was undoubtedly persuaded by Berzelius to investigate ceria further.[35][36][37][38]

Cerium is the most abundant of all the lanthanides, making up 66 ppm of the Earth's crust; this value is just behind that of copper (68 ppm), and cerium is even more abundant than common metals such as lead (13 ppm) and tin (2.1 ppm). Thus, despite its position as one of the so-called rare-earth metals, cerium is actually not rare at all.[41] Cerium content in the soil varies between 2 and 150 ppm, with an average of 50 ppm; seawater contains 1.5 parts per trillion of cerium.[34] Cerium occurs in various minerals, but the most important commercial sources are the minerals of the monazite and bastnsite groups, where it makes up about half of the lanthanide content. Monazite-(Ce) is the most common representative of the monazites, with "-Ce" being the Levinson suffix informing on the dominance of the particular REE element representative.[42][43][44] Also the cerium-dominant bastnsite-(Ce) is the most important of the bastnsites.[45][42] Cerium is the easiest lanthanide to extract from its minerals because it is the only one that can reach a stable +4 oxidation state in aqueous solution.[46] Because of the decreased solubility of cerium in the +4 oxidation state, cerium is sometimes depleted from rocks relative to the other rare-earth elements and is incorporated into zircon, since Ce4+ and Zr4+ have the same charge and similar ionic radii.[47] In extreme cases, cerium(IV) can form its own minerals separated from the other rare-earth elements, such as cerianite-(Ce),[48][44][42] (Ce,Th)O

2.[49][50][51]

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Cerium has two main applications, both of which use CeO2. The industrial application of ceria is for polishing, especially chemical-mechanical planarization (CMP). In its other main application, CeO2 is used to decolorize glass. It functions by converting green-tinted ferrous impurities to nearly colorless ferric oxides.[52] Ceria has also been used as a substitute for its radioactive congener thoria, for example in the manufacture of electrodes used in gas tungsten arc welding, where ceria as an alloying element improves arc stability and ease of starting while decreasing burn-off.[53]

High Ce concentrations occur in soils developed on felsic rocks (granite and rhyolite), intermediate igneous rocks (alkali basalt or syenite), or sedimentary rocks and more recent alluvial and eolian deposits sourced from similar rock types. Examples of such areas include:

Commonly, a 4-step process is used to polish rocks. The first 3 steps start with a coarse, silicon carbide grit and move on to progressively finer grits of silicon carbide with a final polishing step 4 using a polishing compound like aluminum oxide.

If you are unhappy with the amount of gloss you get after completing the 4 steps, you can burnish the stones with soapy water. Cut some shavings from a bar of Ivory soap and put in with your rocks and cover with water. After a few hours, the soapy mix will coat your stones and make them glossier.

We recommend 2 TBS. of grit for Steps 1 and 2, 1 TBS. for Step 3 and 1.5 TBS. for Step 4 polish. Many people think that more grit will do a better job and end up using too much. You will see all kinds of recommendations for how much to use but we have had great results using the amounts above. As people tumble more and gain more experience, they develop their own preferences on how much they like to use. They will also modify based on what rocks they are tumbling.

Below is a close up view of a colony of Dodecaceria concharum emerging from Lithothamnion. On the left is a cryptically coloured sculpin that takes advantage of the background for blending in. See the complete picture below.

The structural change would occur during high energy ball milling and the atmosphere in the vial. Have you controlled the atmosphere in the vial? Oxygen in the vial might be related to the structural change of cerianite. If possible, discussion on the influence of atmosphere should be shown in the text. e24fc04721