>I'll toss my 2 cents into the kitty...
>
>I had my windshield replaced about a year ago. Original 1985 windshield had
>pitting you wouldn't believe -- if driving into the sunset, it was opaque.
>Poor neighborhood kids running and screaming, oncoming cars honking, driving
>with my head out the window, etc.  Got a new windshield and the next day, a
>small rock put a nice set of 3 gouges right in my line of site.  Not
>chips/bullseyes, just gouges.  I've wondered the same thing, is this glass
>just softer?  I've taken bigger hits on my old windshield with no marks.  For
>that matter, I took a foot-long chunk of truck tire tread square in middle at
>highway speed, with no ill effects.
>
>Maybe it is softer.  New regulations?  Cheap glass?  More safe?  I'd like to
>hear from a glass engineer what the various differences in glass are.

Could be this rock was particularly hard. Different types of rock
vary hugely in hardness.