ESO will be revamping the Jewelry crafting system with Update 40.  This will make the Jewelry skill line more consistent with the other crafting skill lines.

I’ll explain it all in the video, but basically grains will go away!  Dust creates grains and grains create plates.  With Update 40, dust will create plates.

For your current inventory, any grains that you currently have will be automatically converted to 1 plate.  Any plates that you currently have will be automatically converted to 10 plates.  

Remember that Update 40 is a free base game update and will be available to all players.