Mining question

[sanecrip]

i found an ore node recently, but now that I'm mining for a second batch I got this weird thing happen. While mining on a same wall, my ores sometimes come at 18.2 and sometimes at 18.7 quality. Is it normal to have the same wall give 2 different qualities?

[Granger]

Ores are softcapped by the tool, hardcapped by masonry somewhat random in quality (even when coming from the same tile).