I have a chimney in Southern California from the early 1940s where mortar has been removed for repointing.

Efforts to identify the mortar at various professional masonry yards
were largely unsuccessful. Only one person (previously in the trade of buying old bricks)identified it as "lime mortar". Whether that fixes the formula to one certainty is beyond my saying.

Question one, is there a way to identify the mortar sample by a field test I can perform? I did put a drop of pool muriatic acid on it and it bubbled pretty well until the acid soaked in. Without expertise or comparative experience with how Portland cement mortars react I can't make an assessment. Any suggestions?

Is there a lab that could do an analysis on this quickly that anyone
can point me to? The job is scheduled to roll at the end of next week.

Question two, assuming that it is lime mortar, is repointing the chimney with Type N mortar a good option? The chimney brick has been identified as "Higgins brick" which was described to me as a softer brick.

I appreciate any experienced advice.