How do I make sure spice mixes don't make my curry grainy? I'm making a curry, with an unknown dry mix of spices (smells remind me of cumin, turmeric and cinnamon) in the form of a powder.

When I've used it before though it's ended up grainy.

Have I been using to much spice mix? It have I not cooked the mix enough? How can I reduce the grainy texture?
I make a homemade enchilada sauce that calls for 4TB of chili powder for 2C of chicken stock.  I make my own chili powder by grinding dried chilis in a coffee grinder that I use for spices.  I make sure that the powder is finely ground. To make sure the final product is not grainy, I cook the sauce for at least 25-30 minutes at a bare simmer, whisking every couple minutes.  The end result is a reduced sauce that is silky and creamy without the graininess.  Even though your powder may seem fine in texture, you might try running through your spice grinder and add some extra cooking and whisking time.