Fluorite is a mineral could be scratched by a penny but not by a fingernail.
<u>Explanation</u>:
Friedrich Mohs was a German mineralogist who developed a hardness scale. The least hard mineral was talc and hardest mineral is Diamond which ranged from Scale 1 to 10. Mohs Hardness scale is a measuring metric which is used to determine the hardness of a metal where one of his standard definitions about “scratching a mineral” using fingernails is very much popular. In that he defined that “Calcite, Talc and Fluorite” can be scratched using fingernails and only “Fluorite” from the given options can be scratched by a penny but not by a fingernail.
