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
In the photo above, the top
scratch was made with a quartz crystal. The next mark was made with a
piece of chert, which is
another form of quartz. The two scratches at the bottom were made with
ordinary chondrites (click on image for enlargement of bottom portion).
Ordinary chondrite 1 left some rusty material along the weak scratch
If you have a rock that
bites into glass and makes a scratch mark like the two at the top of the
photo above, then it contains quartz and it is not a meteorite.
If your rock does not make a scratch, then the rock is still
probably not a meteorite because many terrestrial rocks do not contain
Do Lunar Meteorites Scratch Glass?
let's define terms. By glass, I mean window glass or bottle glass. Some
glasses are harder than others.
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.
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 your
wrong. Lunar meteorites are different than those cheap iron meteorites.
Also, how on Earth can you think a hard rock that survived through
falling through the atmosphere and landing on the ground can't even
scratch glass. Also, most meteorites contain metal. Metal EASILY
scratches glass. Your so called test refers to whether it scratches glass
one way or scratches glass another way so either way even your test
states that it will at least make some kind of scratch.
Also, all meteorites
are NOT even close to being the same so when I'm obviously talking about
a lunar meteorite and you keep referring it as a regular meteorite test
then you're universal way of testing it instead of focused direction is
doomed to fail.
think this is yet another so called expert that go by the book so much
that he doesn't realize that a scratch test was only designed to be a
minor test for only some meteorites and certainly not a test to even
consider ruling it out as not even being a meteorite."
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.
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.
"The scratch test is the worst
test that I've ever heard of regarding meteorites.
Not only do meteorites contain harder than glass substances like iron
metal, but some have even been found to contain HARDER THAN DIAMOND
crystal in them:
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
"Your own website describes and
admits that lunar granite contains more than 60% SiO2(quartz). Quartz
scratches glass. Therefore, lunar meteorites CAN scratch glass. Stop
misguiding people with lunar meteorites!"
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.
"I found out that lunar meteorites
that are Feldspathic Breccias all are rich in Plagioclase Feldspar.
Plagioclase Feldspar is about 6 in hardness. Therefore lunar meteorites
could easily scratch glass because glass is only about 5.5 in
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 do
I stick with everything I say above. If you can make a scratch in glass
like the quartz or chert examples above, then your rock isn't a meteorite.