`   == Origin of ``Quartz`` in References ==   The reference to ``Queensland University of Technology Origin of the word quartz`` is broken in that there is a password requirement to get into QUT—consequently it is useless!     Tensile strength: 48.3 MPa  Pa = Pascals?     Pa = pascal(s)  S.   There is some controversy over density of quartz. Most references I've found say 2.65 g/cm3; see:  for details -   ==Abundance of Quartz in crust== Quartz is a bit of a pain to write about.  It's the most common mineral on earth, and occurs in so many different forms.  The various names are used to mean different things in different contexts, and even then it's rarely rigoursly consistant.  I'll try and point out some of the range of applicability of the various names, and various applicable names.  Oh, and that density listed is not actually for quartz.  It's for fused quartz, which is a glass - unlike everyother type of quartz.  I suspect that confusion is inevitable whilst it is shown on the main page for quartz.   02 Jan 2004  : Actually, quartz is not the most plentiful mineral on earth; that honour goes to plagioclase. I know what you're thinking: sediments (5% of earth's crust) are ~30% quartz, and granite-metamorphic rocks (~30% of earth's crust) contain about 10% quartz. Right? But feldspar is the predominant mineral in granites (at ~60% either plagioclase or orthoclase) is abundant in metamorphic rocks, is also present in sediments, and unlike quartz, occurs widely in the mafic and ultramafic rocks of the oceanic crust. So, bzzzt, quartz is evicted from the island.    ::...although (just for fun) it does specify ``continental crust`` in the article.  )  By the way, for my own...er...interest, do you have a reference for your back-of-the envelope calculation?  It sounds very much like you just whipped it off yourself (although good for you!) but if you have a ref that would be great.  I have seen other numbers cited in German literature.  Cheers,   ==Citrine==  Although most citrine occurs naturally, most is the result of heat-treated amethyst.  So, what is true about most citrine? Is most citrine natural, or is most citrine made from amethyst? Or is it natural-but-derived-from-amethyst-originally? This could stand to be reworded to be less confusing.     :Fixed.  Looks like that was a holdover from an wording change.      ==Pleochroism== It's obvious that author of this article doesn't understand the meaning of pleochroism. Quartz has absolutely no pleochroism. I'll fix it.    == What is the difference between Quartz and glass? ==  I know that glass is amorphous SiO2, is the difference just in a macroscopic perspective of how the crystals are arranged, or is glas SiO2 non-polar while quartz is polar hybridization?  I'm not sure what you're asking here - do you want to know the difference structurally, or how to tell the difference? If you're talking identification, the best way to tell for sure is to chuck it under a petrology microscope and check to see if it's isotropic or not. If you're talking structural differences, well you're right - glass is amorphous at the atomic level - no regular lattice at all.    ==History of Quartz==  ``The exact date, place, and creator of the quartz oscillator are unknown to the public, as this information is classified. It is believed that it may eventually become public as the aftermath of the Cold War wears off``  :- Walter Guyton Cady created the first Quartz crystal resonator along with other colleagues at Wesleyan University in Middletown, Connecticut in 1921  :- George Washington Pierce also help future work in quartz oscillation by designing different types of quartz oscillators, 1923  :- Warren Marrison, a telecommunications engineer developed the first quartz clock in 1927 based on Cady and Pierce's work at Bell Telephone Labratories  http://www.hrw.com/science/si-science/chemistry/careers/quartz/inventors/before.html :  :Thanks, I have modified the article based on your reference.  00:02, 25 September 20