fire clay? California

[colter]

I am looking to mix my own mortar for my dome. everywhere sells what they call fire clay, but one guy I talked with at the local supply store said that its not a true fire clay. here in california you are not aloud to build wood burning fire places any more. so no one sells true fire clay. from what i have read i have seen no mention of different types of fire clay. my question is - can i use the fire clay every one carries, and if not where can i get the real stuff without ordering it over the internet? I live in marin county California.
thank you

[sacwoodpusher]

Muddox makes a fireclay, or mortar clay. It comes out of Sacramento. $5 a bag at Home Depot. It works great. It is probably available in your area at Home Depot too.