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October 15, 2017 Weekly Geology Guest, Corundum

October 15, 2017
Greetings from the Bluff Park Back Porch, way up yonder on Shades Mountain (1,109′) in Alabama:
For the next several weeks we will delve into Industrial Minerals, While they are not glamorous, they are terribly important to our modern way of life. 

Typical examples of industrial rocks and minerals are limestone, clays, sand, gravel, diatomite, kaolin, bentonite, silica, barite, gypsum, and talc. Some examples of applications for industrial minerals are construction, ceramics, paints, electronics, filtration, plastics, glass, detergents and paper.



Corundum is a crystalline form of aluminium oxide (Al

3) typically containing traces of iron, titanium, vanadium and chromium.[2][3] It is a rock-forming mineral. It is a naturally transparent material, but can have different colors when impurities are present. Transparent specimens are used as gems, called ruby if red and padparadscha if pink-orange. All other colors are called sapphire, e.g., green sapphire for a green specimen.”
“Because of corundum’s hardness (pure corundum is defined to have 9.0 on the Mohs scale), it can scratch almost every other mineral. It is commonly used as an abrasive on everything from sandpaper to large machines used in machining metals, plastics, and wood.”
“Corundum occurs as a mineral in mica schist, gneiss, and some marbles in metamorphic terranes

several corundum crystals

Several corundum crystals.jpg
2006 by Ra’ike

Red Corundum = Ruby

before 2010.  Rob Lavinsky, IRocks.

Red Corundum Crystal.

Blue Corundum = Sapphire.

Blue Corundum Crystal.

Corundum Crystals.

Emery nail files: “Emery boards” are a manicure and nail-care product that is made by gluing abrasive papers to a thin piece of cardboard. They obtained their name in the 1800s when crushed emery was used as the abrasive. Today’s emery boards are not made with emery. Instead, many of them have a coarse side of synthetic corundum (aluminum oxide) and a fine side of garnet abrasive. Photo © iStockphoto / Acerebel.
emery boards


List of Industrial Minerals

Editors Note:  It is the intent of this site to keep this discussion as simple as possible, so as to educate the interested general public and not to discuss with the geology crowd the latest geologic theories and nuances.  Thanks, R
“No copyright infringement intended.
The rights belong to their respective owners”
Copyright Disclaimer: Under Section 107 of the Copyright Act 1976, allowance is made for “fair use” for purposes such as criticism, comment, news reporting, teaching, scholarship, and research. Fair use is a use permitted by copyright statute that might otherwise be infringing. Non-profit, educational or personal use tips the balance in favor of fair use.
Author’s Request:  If you see any pictures that you know the source and photographer, let me know immediately.  Thanks!  R

Images have been searched by TinEye Reverse Image Search.

We will now continue down the Industrial Mineral dusty trail and continue with Corundum.
Enjoy the adventure!

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