After finally upgrading to SU Pro 2014 on my Mac, I’ve transferred numerous materials within their sub-folders to ~Library / Application Support / SketchUp 2014 / SketchUp / Materials folder. Now in SketchUp’s Material window, the various sub-folders show as expected in the pop-up menu of the Textures palette, but only a few of the .skm materials show up in each category. Why are not all the materials showing? Also in that same pop-up menu there are a number of categories shown that are not in my Materials folder (like Geometric Tiles and Tonal Patterns. Where do those come from and reside on my hard drive?
those are inside sketchup.app
(SketchUp.app/ Contents/ Resources/ Content/ Materials)
and while nothing is going to explode if you wander in there, it’s really not meant as a place for users to be poking around in…
but inside contents are all the other default materials too… (brick&cladding, groundcover, wood, etc.)…
the problem is if your materials you’ve placed in ~/library share the same folder names as the ones in .app/contents then sketchup won’t read them…
there are some workarounds to this but i don’t think it’s super wise to be publishing them on the internet as a ‘fix’… it’s more of an ‘if you know how to do it then do it’ situation 
anyway, probably the best way to deal with it for now would be to rename your folders in your ~/library to something like my_Brick&Cladding, my_Wood*, etc…
*ha!
Thank you…
Renaming folders works fine.
I don’t see how to get further into SketchUp.app - it doesn’t appear to be a folder.
right click on it then ‘show package contents’
just be aware that any materials/styles/components/etc you may add to the folders in there will be overwritten upon updating the application… for instance, you could add your .skms to the app/contents itself but if you do a reinstall or update of sketchup, they will be wiped out and replaced with the content in the new install.