Mica has been used for many purposes over time and even in my short lifetime I have seen it in toasters, light fittings and as windows in coal-fired heaters.   But what is this amazing mineral?



Mica is a silicate mineral that falls into the phyllosilicate group.   Phyllosilicates are minerals whose structure is made up of silicon and oxygen atoms that form sheets.  Within the structure can sit other atoms including Aluminum (which replaces some silicon atoms), Potassium, Sodium, Calcium, Iron, Magnesium and a host of rarer elements.   Each of the sheets are weakly bonded together and those bonds can be easily broken and so the mineral cleaves along the sheets.  (See our post about cleavage).

The term Mica actually refers to a group of minerals with varying chemistry dependent on the amount of ‘other’ atoms that sit within the structure.   Common micas are Muscovite (KAl2(AlSi3O10)(F,OH)2) – a silver-white mica and Biotite (K(Mg,Fe)3AlSi3O10(OH)2) a black mica.  However, there is a huge range of micas with varying chemistry and therefore colors.

Micas can be found in all three types of rocks – sedimentary, igneous and metamorphic.   Large specimens of sheet mica, used for commercial purposes or for collecting are almost always found in course grain igneous pegmatites.  The largest documented single crystal of mica was found in the Lacey Mine, in Ontario, Canada and it measured 10 m  by 4.3 m and was 4.3 m thick!

Sheet mica, once used as a form of heat resistant glass, has found its real use in electronics.   It resists high temperatures and is a great insulator (and that’s why it is used to hold and  the heating wires in my toaster), but it also takes on electrostatic charges with heating up, and so it is used in capacitors and other electronic components.

Flake mica, often a by-product of the mining or other materials,  is used in the creation of drywall (gypsum plaster sheeting) and as a major additive to paint.  It is used in other building products, such as in asphalt roofing shingles and even as part of the lubricant used in well drilling.

Mica is also often used as a pigment in makeup and candles.

Mica is a very versatile and useful mineral.   Not only that, it is a great mineral to have in your collection….and who does not enjoy just pulling those sheets apart!  Therapeutic Mica.  Maybe that’s my next great idea.

There’s mica in my toaster!

5 thoughts on “There’s mica in my toaster!

  • September 24, 2018 at 10:30 pm

    I’ve read that Mica can be carcinogenic.
    There’s no asbestos in my toaster but it now has mica.

    • September 25, 2018 at 6:47 am

      I have not heard or seen that mica was a carcinogenic. However, any substance that is in a fine powder that you can breathe in may cause issues. This is not the case with the way mica is used in a toaster – it is not in a powder form.

  • December 4, 2018 at 11:44 am

    Hello, thank you for writing this ! I’m currently making some research about toasters, and particularly about insulation. Do you know if mica is used as an insulator between the heating wires and the cover of the toaster ?
    I wonder how the cover, even when in aluminium, stays cool.
    Thank you if you take the time to answer this 🙂

    • December 8, 2018 at 9:11 am

      Hi – I don’t think insulation is used…just an air cavity. But it will depend on the type of toaster 🙂 But its a great question!

      • December 24, 2019 at 7:42 pm

        All the toasters at my Walmart have mica based walls inside them to hold the heating wires up. My problem is that the new toaster I bought puts off a smell. I assumed that after a couple of uses the smell would go away but after a dozen or more toastings the smell is still there. I sure hope that the off gassing will end soon.


Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.