Which one of these four gemstones is not an aluminium compound?

You might be surprised how many gemstones are compounds of aluminium. So, aluminium oxide (a compound of aluminium and oxygen with the chemical formula Al2O3) occurs naturally as the mineral corundum, varieties of which form the precious gemstones ruby and sapphire. The gemstone emerald is a variety of the mineral beryl colored green by trace amounts of chromium and sometimes vanadium; beryl is a mineral composed of beryllium aluminium cyclosilicate with the chemical formula Be3Al2(Si O3)6. However, Amethyst, a violet variety of quartz often used in jewelry, is not a compound of aluminium. Chemically it is Silica (silicon dioxide, SiO2).

More Info: en.wikipedia.org

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17 Comments

Wendye Curran

Amethyst I knew was in another group different from the others. I did forget it was a quartz, but remembered the others were a type of beryl. Kind of a rock person here, but haven't looked at my books in a while. Love questions about rocks and geology of the earth, keep them coming please!

Grant McIntosh

And good to see aluminium spelt correctly.

deborahpmercer

Birthstone for February, so mine!

patrhea

Amethyst is one of my favorite gems.

Jas Newman

Grant McIntosh, It seems you don't agree with your compatriot, Sir Humphry Davy, who originally identified the element and called it aluminum. The Johnny-come-lately name "aluminium" came about to make it sound more like Latin. But then, you probably think "soccer" is an American name for football.

james parrillo

I chose, thinking of the intensity/darkness of color, as I remembered each. I do not know if the thinking was correct, but I manged to choose the right answer. I did not even know that gems are mixtures of minerals. Thank you, Christine, James's wife

Chris Braid

Had to use a 50/50 but guessed right!😁

Louella Wilson

Ruby was the only one that I knew that definitely contained an aluminium compound.

Denise Currie

Almost went for Ruby and thankfully changed my mind at the last minute

Ann Anniss

I'll take any 1 carat gemstone properly mounted in a size 8 ring!!!!

Rhoda Welker Adam

Had no idea. Interesting.

DannyBoy

This was easy for me because I collect gemstones,got it.

smartypants

speaking of amethyst I remembered once reading about Amber which I believe is another gem that is not a compound of aluminium. It actually starts out as tree sap, possibly bugs and even leaves. food for thought.