If you can identify well defined crystal faces, yes:

•Low (b) quartz XX = trigonal (< 537°C)

•High (a) quartz XX = hexagonal (>573°C)

•Cristobalite XX = tetragonal (270°C)

•Tridymite XX = monoclinic

chalcedony is microcrystalline

lechatelerite only by its sturcture (fulgurites)

opal (by it color) amorphous

•Keatite d = 2.50, XX = tetragonal

•Stishovite d = 4.28 - 4.35 , XX = tetragonal

The last two modifications are only found in impactites and rather rare