Discussions

💬 Home 🔎 Search 📅 Latest

╳Discussions

💬 Home 🔎 Search 📅 Latest

Groups

Recent Images in Discussions

Identity HelpBlue mineral What is it?

12th Dec 2016 04:04 UTCNancy Gerlach

I found these blue boulders in the wall of a wash in Arizona today (near Lake Pleasant).

Can anyone help identify these?

Thanks-

Nancy

12th Dec 2016 05:00 UTCMatt Neuzil Expert

At first i thought they looked like sodalite. But now i think something else. Do you have some sort of thick glass? Scratch the blue mineral across the glass. Does it scratch the glass?

Try and do some general tests that help id minerals.

Check Mohs hardness (scratching the glass will be a start), check the streak by scratching on unglazed porcelain.

12th Dec 2016 05:56 UTCMark Heintzelman 🌟 Expert

Visually, it does remind me of samples I've seen of Dumortierite, more specifically from Madagascar

Hardness for Dumortierite is about 7 - 8, for a sodalite group mineral or other feldspathoid, is only about 5½ - 6

MRH

12th Dec 2016 10:48 UTCPeter Nancarrow 🌟 Expert

I agree with Mark that it looks very like dumortierite. Cordierite is another possibility if the hardness is similar to dumortierite.

Both are commonly found as massive material and bluish in colour, but they are fairly easily distiguished by their SG difference. Dumortierite is much denser, with SG of about 3.2 to 3.4 (so a large piece feel distictly heavier than a similarly sized piece of quartz) whereas c.'s SG of about 2.6 means it feels about the same weight as quartz. Sodalite has lower SG.

If you have access to any optical testing equipment such as a polarising microscope, simple optical tests will also help to tell them apart. D. has distinctly higher RI and birefringence than cordierite, and although they are also both strongly pleochroic, they show diffrerent colours.

Pete N

12th Dec 2016 11:08 UTCNancy Gerlach

-- moved topic --

12th Dec 2016 13:58 UTCRolf Luetcke Expert

Nancy,

I have collected quite a bit of dumortierite a bit farther South but it sure looks like dumortierite as said above.

Actually quite nice for much of the material I have seen so good find.

Rolf

12th Dec 2016 14:25 UTCMatt Neuzil Expert

Nancy, do you trade or collect minerals? If you do, I'd be happy to trade for a piece. You can click on my name to contact me.

12th Dec 2016 18:08 UTCNancy Gerlach

Thanks so much everyone! I have to get my "identification" education up to speed if I'm going to continue playing with rocks. Plus I've screwed up many minerals by cleaning them incorrectly (because I didn't know what the heck they were). I don't have any unglazed porcelain but I'll get some and do the streak and get back with you.

Matt- I do collect and would be happy to trade. I'll contact you soon.

Peace - Nancy

12th Dec 2016 21:51 UTCIan Nicastro

I agree that this is logically likely Dumorterite, however it does not look like exactly like the typical massive mostly opaque blue Dumorterite that we see from the southern CA side of the border. I know that just across the border that same type of material exists in AZ, as I have an acquaintance that had a claim on the AZ side of the border for Dumorterite... but oddly mindat has no photos of lapidary grade blue Dumorterite from AZ. I've never ever heard of massive blue Corderite being found in that area. You really need to do a mohs hardness test on this to make sure it's not Apatite or something else just in case.

12th Dec 2016 23:57 UTCNancy Gerlach

There were quite a few outcrops of this as we went but each one was different- the darker the material the softer and more breakable... the bluer and waxier the harder they were to break.

Thanks for the confirmation-

Nancy

13th Dec 2016 03:57 UTCD. Peck

Nancy, Specific Gravity is a very useful property, if you have the balance to do it. It is often quite definitive. The specimen has to be free of other minerals, so it is better to work with relatively small pieces.

Mindat.org is an outreach project of the Hudson Institute of Mineralogy, a 501(c)(3) not-for-profit organization.
Copyright © mindat.org and the Hudson Institute of Mineralogy 1993-2024, except where stated. Most political location boundaries are © OpenStreetMap contributors. Mindat.org relies on the contributions of thousands of members and supporters. Founded in 2000 by Jolyon Ralph.
Privacy Policy - Terms & Conditions - Contact Us / DMCA issues - Report a bug/vulnerability Current server date and time: May 7, 2024 16:54:18

Go to top of page