METEORITE OR METEORWRONG?
Meteorites do not contain any substantial amount of quartz, whereas quartz is common in many terrestrial rocks. Quartz is harder than any of the common minerals in meteorites. Quartz is so hard that it will easily make a deep scratch in glass. Even if you press hard, a meteorite will at best only make a weak scratch mark. (Use a sharp edge of the rock.)
Do Lunar Meteorites Scratch Glass?
First, let's define terms. By glass, I mean window glass or bottle glass. Some glasses are harder than others.
Do lunar meteorites scratch glass? I've tried it with a couple. They don't scratch glass any better than the ordinary chondrites above. Quartz bites into glass; you can feel it and you can hear it. Chondrites and lunar meteorites slide across the top. If you press hard, the meteorite breaks and maybe a weak scratch happens in the glass.
But, an opinionated correspondent thinks I'm wrong. Below are excerpts from four e-mails he sent me in one day after I told him that it looked to me, from a photograph he sent, that his rocks contained quartz. I suggested that he try the scratch test.
I think he's wrong. First, he confuses mineral hardness, an intrinsic property of minerals, with rock coherency. Lunar meteorites are coherent, but the three main minerals of which they are composed, plagioclase feldspar, pyroxene, and olivine are not as hard enough to scratch glass.
Also, metal in meteorites is not hard. I've also tried scratching glass with the sharp edge of Gibeon, and iron meteorite that I have here in my office. No scratch. Some steels may be harder than glass, but the iron-nickel metal in meteorites is not. Besides, lunar meteorites contain at most only a few percent iron-nickel metal.
Yes, some chondrites (but, I thought we were talking about lunar meteorites?) contain really hard stuff like silicon carbide, diamonds, and boron carbide. But these rare minerals are present as microscopic grains in minute quantities, not enough have any effect on the meteorite's abrasiveness.
Yes, there are some rare granites in the Apollo collection. They're small. I'm not even going to think about trying to scratch glass with one (and I've got several here). But, there still hasn't been a lunar meteorite that is a granite. Silica minerals (quartz, tridymite, cristobalite) do occur at trace levels (<1%) in some lunar meteorites but, again, not in high enough levels to have affect the rocks abrasiveness.
This is better (and read this).
But, try it! The reality is that plagioclase feldspar doesn't bite into
glass. Plagioclase is brittle. If you press hard, it breaks. Quartz doesn't