As far as the countable/uncountable issue is concerned, you are correct, at least according to my usage. A large quantity of cement A large amount of cement A large quantity of bricks (or A large number of bricks ) " A large amount of bricks " doesn't sound right to me, but it's not uncommon to see instances of this usage from native speakers, and these people obviously don't see any problem with it. In the countable sense, "quantity" tends to be used for objects that aren't viewed as being particularly individually distinctive.
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