FMF - Friends of Minerals Forum, discussion and message board

[Sam Durrant]

Good morning

I would be grateful for any assistance in identifying the following mineral. It has a light heft, grey metallic surface with distinctive v shaped regular markings. There are reddish areas similar to haematite but I have discounted that based on the form and low heft. The material seems brittle and split when I attempted a streak test. I do not know the locality but strongly suspect it is a mining related mineral. Dimensions are 4.5cmx1.5cm. Thank you

[SteveB]

I’m thinking it might be something in the mica family. Hard to tell from the photos but I have specimens that have a metallic sheen to the but are very light.
Can you break off any plates from the surface, or is the surface a single intact piece? Run you finger in one direction then back the other direction… is it smooth one way and sort of rough or catchy the other way? This is what I feel with mine that I haven’t identified yet but it’s mica/biotite family.

[Sam Durrant]

Thank you for your reply. Yes, the plates are overlapping a bit like fish scales and will flake if prodded. I will look through images of different mica types, it's not a mica form I have seen before. Much appreciated.

[SteveB]

Yes! Fish scales perfect description. Muscovite seems to be more what we’re looking towards what we both have. Mine is somewhere in my unsorted/ unlabeled specimens and is greenish.

[James Catmur]

A mica of some sort - hard to know which as there are so many types of Mica. Wiki says:

https://www.wikiwand.com/en/Mica

[SteveB]

I agree with your feeling it’s a mining related mineral. Mica in various forms is mined and used in many products. Crushed it is mixed into cosmetics to give ladies a “glowing” look since the mica reflects light softly when powdered can also be added to paints and inks to create reflective effects and metallic car paints. If I recal correctly it’s one of the most common minerals on earth. Look closely at any patch of dirt and any glints of sunlight are fragments of mica, it breaks so easy and forms as flare platelets so it’s easy for wind and water to carry it so it gets everywhere. Yours appears to have grown it’s mass as columns of the platelets.

[James Catmur]

We used to find plates of mica every time we dug a hole in the fields on the farm. I think the biggest was about 20 cm across. I still have some of them.

[Matt_Zukowski]

I see no reason to assume that this is related to mining. It could be mica shist, a common metamorphic rock. I hiked around the Grand Tetons one summer, and igneous mica that looked like this was all over the place.