All 4 Uses

although
in
Blink, by Malcolm Gladwell
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By that I don't mean that experts like different things than the rest of us—although that is undeniable.†
Chpt 5 *

although = even though -- used to connect contrasting ideas
And, like the experts, the students thought that Acme and Sorrell Ridge were markedly inferior to the others, although the experts thought Sorrell Ridge was worse than Acme, while the students had the order the other way around.†
Chpt 5
He is clean-shaven, with closely set eyes and thick, prominent eyebrows, and although he is of medium build, he seems much larger: there is something stubborn and substantial in his demeanor.†
Chpt 6
It's not just because of the dangers of hitting some innocent bystander during the chase, although that is clearly part of the worry, since about three hundred Americans are killed accidentally every year during chases.†
Chpt 6

Definitions:

(1) (although)
even though -- used to introduce an idea that contrasts with or makes the main statement surprising

At the start of a sentence, although can play a role similar to words like however, yet, still, even so, on the other hand, or nonetheless—all of which signal contrast. In the middle of a sentence, although can sometimes be used where but or though might also work, but though or but often sound more natural. For example, "She's a great teacher, though not the most popular" is usually smoother than "She's a great teacher, although not the most popular."
(2) (meaning too rare to warrant focus)