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quartz
A topaz
The unknown mineral is not a mineral, or the pieces being scratched or doing the scratching are not freshly fractured or cleaved surfaces.
It can be scratched by a diamond, corundum, topaz, and quartz.
orthoclase
not diamond
minearls
Diamond will scratch anything.
A few minerals that do not scratch glass come to mind . . . talc, asbestos, mica, for instance.
n
It would have to be 5.0 because glass has a hardness of 5.5 and an iron nail has the hardness of 4.5
apatite with a steel knife feldspar with window glass