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Identity HelpWhat makes blue colors?

6th Nov 2016 01:58 UTCSophiaJoy MB

What causes the blue in blue Calcite?

What causes the light blue in Blue Lace Agate?

I've been looking for information about causes of colors in minerals...

Thanks for your help!

6th Nov 2016 07:23 UTCJoel Dyer

Hi SophiaJoy,

There are several reasons for colours in minerals / gemstones. Mains reasons include:

- Certain elements in the mineral's / gem's chemical composition (in the case of some minerals)

- Defects in the crystal structure of the mineral

- Inclusions of foreign material in the mineral

- Damage in the crystal structure caused for example by natural radiation

- Trace elements - for instance "transition" elements or "REE" elements

- Other scattering / refraction of light inside the mineral, several reasons here

Here are some links:

http://www.webexhibits.org/causesofcolor/6.html

http://www.compoundchem.com/2014/06/29/what-causes-the-colour-of-gemstones/

http://nature.berkeley.edu/classes/eps2//wisc/Lect7.html

http://www.gia.edu/gems-gemology/fall-1987-color-gems-fritsch

Cheers,

6th Nov 2016 18:06 UTCElise Skalwold

For an in-depth look at the causes of blue color in minerals (as well as serving as an overview of the causes of color in general), you might seek out this paper which we were invited to write for the special Blue Minerals issue of Rocks & Minerals magazine: http://www.rocksandminerals.org/Back%20Issues/2016/January-February%202016/blue-minerals-exploring_abstract.html

Skalwold, E.A. and W.A. Bassett. (2016) Blue minerals: exploring cause & effect. Rocks & Minerals, Vol.91, No.1, pages 61-75. The whole issue is great and can be ordered through the link, or you can obtain the article through your library.

Very best wishes,

Elise

SophiaJoy MB Wrote:

-------------------------------------------------------

> What causes the blue in blue Calcite?

> What causes the light blue in Blue Lace Agate?

>

> I've been looking for information about causes of

> colors in minerals...

>

> Thanks for your help!

7th Nov 2016 01:25 UTCSophiaJoy MB

Thank you very much for the links, Joel and Elise!

Regarding Blue Calcite, some say the blue color is caused by strontium. Is it right?

I thought strontium was not safe to touch...

7th Nov 2016 01:51 UTCReiner Mielke Expert

It is not what is in it but how the elements are combined that determines if it is safe or not. For example table salt contains sodium, a flammable dangerous metal and chlorine, a poisonous green gas but you can safely eat it.

7th Nov 2016 02:29 UTCDoug Daniels

For that matter, calcite also contains calcium, which is also not very safe to touch (but safer than strontium). But as Reiner said, it has more to do with how the elements are combined.

8th Nov 2016 14:25 UTCSophiaJoy MB

Thank you so much, Reiner and Doug! :-)

OK, so, Blue Calcite doesn't have strontium...(tu)

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