For example: Color? Hardness? Streak Color? Metallic or Nonmetallic luster? Fracture of Cleavage? Magnetic or Nonmagnetic? Reacts to HCl?
Topaz is a hydrogenated or fluoronated aluminosilicate whereas quartz is silicon dioxide (Yes, Viriginia, there is a silicate mineral called quartz). The smoky variety of quartz is due to impurities and I believe the smoky variety of topaz is due to the same thing. The easiest way to distinguish them is by a hardness test: topaz (Mohs hardness of 8) will scratch quartz (Mohs hardness of 7), although the amount of force needed might be greater than what some people can exert. Topaz crystallizes in the orthorhombic system (where every angle is ninety degrees) and quartz crystallizes in hexagonal crystals.
This Site Might Help You. RE: Whats the main differance between smoky topaz and smoky quartz.? and how can you tell them apart in jewelry?
Ugly Fish's suggestion of scratch test is good. Quartz is softer and will be scratched a bit by topaz - Quartz 7 , Topaz 8. So get a bit of quartz and see if you can scratch it with your stone. Topaz fractures very easily though so be careful. Topaz is much more dense than quartz , should be about 3.5 gms/cc but this is not really a lot of use to you unless you have accurate ways of measuring volume and mass or big bits of topaz. Best of Luck
We are talking about two quite different minerals. First quartz in a crystalline form. Quartz is Silicon Dioxide SiO2 (not a silicate!) - smokey only refers to its colour which in this case brown to nearly black which is produced by millions of years exposure to the background radiation in its parent rocks. It is also produced artificially by putting clear quartz into a cobalt 60 radiation chamber which does the job in about an hour. The properties of quartz are :- Refractive index 1.544 - 1.553 Specific Gravity 2.65 - 2.66 Hardness 7 Topaz. This is Aluminium silicate Al2(OH,F)2SiO4 which contains variable amounts of OH and F. The colours are varied but it never produces the dark browns of Smokey Quartz. The term Smokey Topaz is in fact a misnomer coined by less honest members of the jewellery trade to sell cheap quartz as a much more expensive to people who do not understand gem stones. It is a term that should NOT be used. Topaz constants are :- Refractive Index 1.607 - 1.619 to 1.629 - 1.637 S.G. 3.50 - 3.60 Hardness 8 To sum up if you have a stone that is some shade of brown (may have a greenish yellow tint) to nearly black it is not likely to be any form of topaz. Testing the Refractive Index is a sure fire way to tell. Be careful of hardness testing as topaz splits very easily. and you may wreck a good stone. If its cheap its not topaz believe me.
