First, it's the largest 'naturally occurring' piece of iron at the earth's surface. It weighs somewhere around 60 tons, and it's 84% iron. Which makes a case of it being a little special just because nobody farmed it out and sold it off.
Second, when it fell to earth (somewhere around 80,000 years ago) it fell unusually slowly. Arguably this is because of it's flat shape, meaning it skipped across the atmosphere until it slowed down enough it landed without shattering into a bunch of smaller pieces. It's always the largest single-piece meteorite on the planet.
There are all sorts of other cool bits about it on the Wikipedia page here, but I thought it was worth sharing just so we could all imagine watching a giant hunk of metal skipping across the atmosphere like someone's throwing pond stones at us.
We are mostly water.
Come back next week, we'll have a guest post on Friday and on Wednesday we'll either talk about creating dynamic women in fiction, or creating a bestiary as a tie point for your universe.