Quartz and fluorite are two very different minerals, each with a different hardness and crystal structure, although on the surface they look very similar. Both rocks come in clear or white tones, as well as purple, pink, blue and green. The visual similarities make them difficult to tell apart, but you can distinguish the two minerals with some simple tests.
Determining the Difference Between Fluorite and Quartz
Scratch the rock with a utility knife to determine its hardness. Hardness is determined using Moh’s Scale. Fluorite is a four on the hardness scale, whereas quartz is a seven, which is much harder. Fluorite will scratch if you scratch it with a normal knife blade because a blade has a hardness of 5.5. Quartz will not scratch if you try to score it with a knife blade.
Scratch a piece of glass with the rock. Fluorite will not scratch glass because it is not hard enough. Quartz is harder than glass and will scratch the glass.
Use a hand lens to examine the crystal structure of the rock. If possible, use a hammer and a piece of fabric to break a small piece of the mineral. Put on your safety goggles and place the fabric over the rock. Hit it with the hammer. Quartz will break into shards that are curved, while fluorite crystals have a clean, eight-sided break. If the rock is unbroken, the fluorite crystals will often form cubes.