Everyone is saying it is grain size, but you asked how to tell the difference, I bet you want VISUAL clues. Quartzite looks like a plain whitish colored ROCK. It typically stands out from the surrounding rocks because of the quartz content, but you would never mistakenly pick this stuff up and put it in your mineral collection. It can be all sorts of colors because of mineral impurities, however, the granular texture is a giveaway. Solid quartz is not going to be granular in nature. Quartz is typically going go be very glassy, with broken surfaces similar to broken glass. Often times masses of quartz will have open voids where crystallization can occur. If you google image source both words, you'll have a great visual understanding.
Your question is a false dichotomy... quartzite (metamorphic rock) is composed of quartz (mineral). Quartzite is formed when a quartz arenite (sandstone) is metamorphosed under high temperature and pressures. The original quartz grains recrystallize, creating an interlocking mosaic . This explains why, at the microscopic level, you are having difficulty distinguishing the two. They are identical!
Crystal size. Quartzite is fine grained.
The only approach i will tell the difference between hiccups and kicks is how lengthy they last. In the beginning for the first 30 seconds hiccups feel just like kicks so i'll simply anticipate the little one is relocating, however then i'm going to detect a pattern and if i will be able to predict when the following little bump is i know she's hiccuping. Identical to when that you can inform the pattern of your hiccups, your youngster's hiccups will be bump pause bump pause.. Ect.
Texture. Quartzite is noticeably granular. Qurartz is glassy. .