Re-pointing with a strong mix like 3/1 sand and cement can often cause damage to the stone work. A 1/2/9 cement/lime/sand is usually recommended. In a more exposed area use1/1/6. Pointing should be seen as a sacrificial part of the wall.
If you use more cement instead of lime, the mortar won't allow any moisture to evaporate through the joints. In freezing conditions this can cause the edges of the stone to break away. Also a lime mix is less likely to crack and allow water penetration. The down side to a lime mix is that it's less durable. In exposed areas near the coast it's less effective.
He may have asked for a photo to see what type of stone it is eg. limestone, sandstone or granite, or what type of pointing such as ribbon or recessed.
My son is coming at the weekend and he is bringing his camera so I will post a photo and you might have a better idea. You sound to know a lot about it so I will be back in touch
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