• Register

Information for users from the old Q&A site
If you have an account from our old Q&A site, your account was transferred over, but you need to reset your password and confirm your email address.
Reset Password here
Confirm Email here

2,234 questions

3,904 answers


105,642 users

the chemical formula of Chlorospinel gems .

0 votes

Spinel occurs almost every color, and forms gems of all colors... Would you please tell me .The chemical formula of chlorospinel gems. I'm looking forward to hearing from you. Thanhk you.

asked May 20, 2012 by maicindy2008 (240 points)

7 Answers

0 votes

Chlorospinel is an iron-rich spinel - i think its formula is Mg(Al,Fe+3)2O4

answered May 21, 2012 by hershel (52,780 points)
0 votes

@ Hershel : Chlorospinel contain element copper. Is the chemical formula Mg(al,Fe3)2O4 right?? You can look for the information at : http://www.minerals.net/mineral-variety/Mineral/Chlorospinel.aspx Thank you very much!

answered May 31, 2012 by maicindy2008 (240 points)
0 votes

Interesting. It says there its color is caused by traces of BOTH iron and copper. Though I think it is highly unusual for there to be a significant enough copper content to include it as part of the chemical formula. It is most likely only minor traces of copper that provide the color. I have never heard of a copper-rich spinel, so that is most likely just minor traces.

answered May 31, 2012 by hershel (52,780 points)
0 votes

@ Hershel : Some mineral may contain an element that partially replaces an inherent element.. Therefore, an additional formula, known as the variable formula, to state the occasional presence of these elements. Http://www.minerals.net/resource/chemical properties.aspx So, your chemical formula of Chlorospinel is Mg(Al,Fe+3)2O4 And the variable chemical formula of Chlorospinel is (Mg,Cu)Fe2O4 Is it right ? I hope to receive your reply. Thanks very much.

answered Jun 3, 2012 by maicindy2008 (240 points)
you are right
0 votes

Technically you are right that the variable formula should be (Mg,Cu)Fe2O4, but I think in this case the the presence of copper is very insignificant and only qualifies as a trace or impurity, and is not enough to affect its chemical formula. However, the minute trace or impurity can still act as coloring agent even without a significant presence in the formula.

answered Jun 5, 2012 by hershel (52,780 points)
0 votes

@ Hershel: Please tell me, What is the RI and SG of Chlorospinel ? Thank you.

answered Jul 24, 2012 by maicindy2008 (240 points)
0 votes

Not sure exactly, but I would guess it would be very close to spinel with has an RI of 1.712 - 1.736 and an SG of 3.5 - 3.7 (though may be very slightly higher since Cu is a heavier metal than Mg

answered Jul 24, 2012 by hershel (52,780 points)