I use mica powder as a base in some of my filaments, but it is really hard to extrude under compression since mica is a non-newtonian fluid. I find that I have to extrude slower to get it stable. The other problem is mica absorbs more heat and I have to run at a hotter temp to get it to flow right.

Mica is great, it looks excellent, and has a great shimmer.

A good place to get mica pigments from is justpigments.com

Keep up the experimenting! Cheers!

36 colors, 5g per color.  I started with Red Golden:

I had to order a new scale because I do not believe my old one was accurate for such small amounts of powder, but my old scale was telling me it was 1g of powder used with 750g of 4043D.  I believe this was too much still as the powder is very shimmery but that doesn't show up in the filament - I believe it would show up more if I used less powder and let the plastic be slightly more transparent rather than opaque.

Here is the powder mixed with the pellets:

Here is what it looks like in filament form:

And here it is in a print test to see what it ends up looking like in a model:

What size nozzle are you printing with? That stuff looks terrifying from a clogging perspective!

Really cool stuff.

.4mm.  I have had some jams, but it seems to always be when the filament has one of the white (unmelted look) blobs and the diameter spikes up.  The Capricorn PTFE will catch any small section over 1.9mm and stop feeding.  I know - 'why don't you just not use the Capricorn PTFE' - that's because a jam in the Capricorn is easy to fix - you just release tension and pull it back out.  If your extruder tries to push a section of filament down that's too large for the hotend it causes a much worse jam (even if it's much less likely to happen, I don't think I'm spiking quite that much on the white sections).

Edit: Ok, yeah, I did run into some nozzle clogs with the coffee.  Cinnamon particles were quite a bit smaller.  Also noticed something else odd - cleared out all the particles in barrel and am getting clear PLA again (had to increase temperature and drop distance as the pure PLA seemed to come out as a much larger diameter), but I have a little bit of the PLA seemingly sticking to the nozzle and suddenly/randomly coming out onto my filament when it feels like it. Almost like the furr described in this post: http://www.soliforum.com/topic/15873/tpv-irogran-a85/

Edit 2: Diameter consistency improved significantly after I moved my cooling fan down.  I think it have just been lightly grazing the very outermost part of the die and increasing friction there.

Edit 3: It had improved by moving the fan, but I still had this odd spiral pattern.  Seemingly with less cooling it was less obvious, but I actually stood there and saw what looked almost like a 2nd filament strand come out of the nozzle, and wrap itself around the primary strand of filament - a spiral blob.  I tore my Filastruder down to the barrel and augur, discovered my augur was not sticking out of my barrel by 2-10mm so I added some washers as spacers.  I put it all back together, and now it seems they actually have gone away.

Really cool stuff.

I still have random spots where I get white blobs that slightly increase diameter, almost like raw unmixed pellets are somehow making it through.  Yep, it smells like coffee when printing.

It's actually a pretty color - the cinnamon stuck to the pellets pretty easily just as is.  My diameter is a bit off, so I have had some jams when the diameter goes over 1.9mm (Capricorn PTFE liner on hotend so it's 1.9mm ID), but I think it's more of an environmental thing than the addition of the cinnamon.  Kind of hard to get the pellets dry in a 95F room at 82% humidity like it's been here lately, or to cool PLA properly with room temperature air.

This was obviously for play filament, not for big useful mechanical parts, so in that spirit - I present to you - Tiny 'Cinnamon' Rick:

Model: https://www.myminifactory.com/object/3d-print-55133

Yes, the room does smell like cinnamon, hot cinnamon, maybe burned cinnamon depending on what temp you use for your PLA, but the smell is not present in the finished item unfortunately (unless you put it in your car on the dashboard, then when it starts to melt you'll probably get the smell again).