I first encountered the term "pitchblende" when I was a kid, probably in some old science fiction book or other. I knew it had to do with uranium, but wasn't quite sure exactly what it meant 'til I looked it up recently: it's a mineral that contains radium and uranium, the "pitch" part referring presumably to it looking like pitch, and the "blende" part referring to, well, blende.
Which leads inevitably to the question: What's blende?
MW11 to the rescue: "blende," it turns out, is a synonym for "sphalerite."
And now you know as much as I do.
Well, okay, I know slightly more (unless you already knew this), because I have cleverly followed the dictionary's link to "sphalerite" and learned that it's a zinc ore, "composed essentially of zinc sulfide."
Turns out "sphalerite" derives from Greek "sphaleros" meaning "deceitful," because sphalerite is "often [...] mistaken for galena." I'm amused that whoever named it (around 1868) felt that its deceitfulness was its most important property, and felt so strongly about that that they named it in Greek.
At any rate, this obliquely reminds me of one of my favorite dictionary definitions: once, years ago, I looked up an unfamiliar term and found a definition that I remember as having said "a specular variety of galena, found most often in Derbyshire." Which sounded approximately like gibberish a la "The gostak distims the doshes" to me. Sadly, I don't recall what the word was that had that definition, and a web search isn't turning up any promising candidates.
Now I suppose I have to tell you that "galena" is apparently a lead ore, lead sulfide.
If this keeps up, I may have to retitle this blog to "Rocks & Stuff."