Without a picture it's hard to tell, but perhaps that is too many different woods.

Okay, photo loaded. best M

Ash being a light wood but can be hard to stain in a darker stain since it's such a dense wood - I would consider staining with Minwax English Chestnut # 233 add coats until it gets dark enough to match adjacent wood stain , also consider a very flat sealer ( such as tung oil or satin poly no shine is important against the flat finish of brick

Well, thanks so much. I was wondering about oil. I guess you keep applying until it gets to the desired darkness. Do you think an oil is protective enough over a fireplace? (I don't think there's a significant amount of heat that escapes as its a propane fireplace). Best

There is no problem with the stain and fire - done all over the world -let stain dry between coats once the stain starts staying on top and doesn't sink into wood you will have reached max. saturated coverage possible