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How Can I Tell the Difference Between Fluorite & Quartz?

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.

Things You'll Need

Quartz sample
Fluorite sample
Utility knife
Hammer
Safety goggles
1 foot of fabric
Piece of glass
Hand lens

Instructions

Determining the Difference Between Fluorite and Quartz
- 1
  
  Use a knife to scratch the minerals.
  
  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.
- 2
  
  Use the rocks to score glass.
  
  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.
- 3
  
  Use safety precautions when working with a hammer.
  
  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.

Rocks & Minerals