Granite and Quartzite Compared for Dummies

granite dome

We often complain that the minimum word count imposed by the masters (chief demanders?) of eHow.com caused much of what we consider to be the site's stupidification of the internet. That's because so many of the scientific illiterates and "un-handy" freelancers could address the basic question, but — forced by the MWC to keep writing — made a hash of the less basic details. That's the problem with today's nominee, Jay Leone of Sciencing.com and the post "Difference Between Quartzite & Granite": he just wouldn't shut up.

For starters, the difference is pretty simple: granite is an intrusive igneous rock that contains 35% to 60% quartz plus relatively large amounts of feldspar. Quartzite is a metamorphic rock whose protolith¹ is quartzose sandstone. Most quartzite has a high quartz content, in the neighborhood of 90 to 95% quartz. Leone (more or less) said that, but it was only 50 words or so and he needed 300 to 500. What to do, what to do...
Well, what Jay did was attempt to reword a boatload of information he didn't understand, beginning with commercial posts from countertop vendors. We guess no one told Leone that not all "granite" countertops are granite... Whatever the case, here are some samples of the bushwa that Jay pounded out:

• "Quartzite is a metamorphic rock that forms from the joining of sandstone and quartz under intense heat and pressure." — The "joining of sandstone and quartz"? That's a weird way to describe recrystallization!
• "Sandstone is often compacted into quartzite when continents collide, filling in empty grains of sandstone with quartz. " — This is some idiot's version of filling the pore spaces of quartz sandstone with quartz overgrowths.
• "Granite forms at greater depths than quartzite,..." — 'Tain't necessarily so...
• ""Quartzite offers an approximate value of 7 on the Mohs scale while granite offers a hardness value of between 6 and 6.5 on the Mohs scale.  —  The Mohs scale is for minerals, not rocks. Since it's mostly quartz, the hardness of quartzite is clse to 7, but claiming that granite has a harness of 6? Utter  bullshit.
• "Any rock that... offers an alkali-to-feldspar ratio between 65 and 95 percent is defined as granite. " — WTF is this "alkali-to-feldspar ratio"? In reality, the criterion is a minimum of 35% alkali feldspar.
• "Biotite, magnetite, garnet, zircon and apatite may also be involved in the formation of granite if the materials are present. " — What "materials" might those be, Jay?

Therein lies the danger of letting journalism and English graduates write about any science beyond what they studied in middle school, because chances are quite good that they will not understand the material in their references. eHow's demand that they keep writing after they've exhausted their knowledge has produced many a Dumbass of the Day, much as it did to Leone.

¹ The protolith is the rock type before metamorphism occurs.

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