just got me a new wood fireplace

Hi there. I decided 2 weeks ago i wanted a fireplace and last week i got one. Its a smaller one, but it puts out alot of heat. Enough to heat my 2000 square' home. I cuts some old fir trees on my property last winter and thats all i have to burn for now until i get some time off from work to buy some more. I know its not quite seasoned enough, but it seems to burn ok. However, im concerned about the large amount of pitch that is in this fir and if its harmful to my chimney. Any opinions and advice is appreciated.