At Tom's suggestion I googled for "hard maple". Google's "I'm feeling lucky" returns an hardwood.org <a href="http://www.hardwood.org/species_guide/display_species.asp?species=hardmaple">page</a>. Between that page and the "Soft Maple" link it contains, the distinctions previously mentioned in this thread seem to be correct.
I've been known to dwell on minute details, so I can appreciate this new tack, but when most people that even understand there's a difference between "hard" and "soft" maple talk about the difference, it's not strictly density they have in mind. Rather the intended use for the wood.
I guess for me to quibble <i>against</i> the small details proves I'm not entirely opposed to situation ethics. :<tt>)</tt>
Something I find interesting is in my copy of <a href="http://www.outdoorshub.com/Trees_of_the_Eastern_and_Central_United_States_and_Canada_0486203956.html">Trees of the Eastern and Central United States and Canada</a> by William H. Harlow, the author states<blockquote>"Michaux wrote that hard maple wood can be separated from that of soft maple by a drop of any ferric salt solution on the end grain. Hard maple turns a greenish color, whereas soft maple shows a bright blue. On some 50 samples of each, the author finds that all the hard maple turn greenish, all the soft maple <i>sapwood</i> become blue, and about one-half of the heartwood samples tested are also dark blue, the remainder dark greenish blue. The test appears to be permanent, since after 6 months the blocks can still be readily separated by color."</blockquote>Of course that was about 50 years ago; I wonder if the difference can still be noted on his samples...
Glen