4. Easily scratched by a fingernail Feels “greasy” Softest mineral Barely can be scratched by a copper penny Scratched by Fluorite but not Talc Acid makes it fizz and has double refraction. Another name for a ruby or sapphire Can be scratched by minerals that are 9 or 10 Scratches Topaz Scratches quartz, streak plates, and glass Scratched by Corundum Easily scratches both glass and steel Silicate, abundant, found in a variety of colors Scratched by Topaz but not Feldspar Easily scratched by steel file or glass “Glows” under a ultraviolet (black) light Can be scratched by a fingernail Scratches talc Found near Saltville Scratches glass but does not scratch steel Scratched by Quartz Found in granite Scratches everything Hardest mineral Only diamonds can scratch it Can be scratched by steel file or glass Will scratch Fluroite but not Feldspar