Iridium
is used in pen nibs because it's so hard. But it's not necessarily very pure. It's also very expensive.

To do accurate measurements, you need something like 99.9999% purity, which is very difficult to achieve.
( K2k6 has a proper job these days, Thu 11 Jun 2009, 10:56, 2 replies, latest was 17 years ago)

Hmmm...
Would a sword made of iridium keep a good edge?
( Cawl, Thu 11 Jun 2009, 10:57, Reply)

I've been reading about this...
Hardness is not the same as strength. Or not the same thing as toughness...hang on a minute...

Oh, that's right - something can be hard, but not very strong, if, say, it's brittle. Iridium is probably used in pens because it keeps its edge, but is quite brittle.

I don't really know - try slashing someone's face with your pen and see how the nib fares...
(LongJohnBaldry, Thu 11 Jun 2009, 10:59, Reply)

Hmmm...
Incredibly well, in fact.
He's now in the back of an ambulance.
( Cawl, Thu 11 Jun 2009, 11:03, Reply)

*crap joke alert*
Well, an iridium-edged sword might be a fearsome weapon. But the iridium tipped pen will still be mightier.

...Still, it's obviously done the do on him - what state is your pen in?
(LongJohnBaldry, Thu 11 Jun 2009, 11:47, Reply)

Yes it would keep a sharp edge
but I don't know about its brittleness, as Mr Crow said above. So it may lose its edge if you use it, just by chipping bits off. Also, it would be an extremely heavy and unwieldy sword.

A hardened steel sword with an iridium edge might be a good compromise.
( K2k6 has a proper job these days, Thu 11 Jun 2009, 11:03, Reply)

They use iridium
in sunglasses lenses too for some reason

doesn't it only come from meteorites?
( Vipros. clever got me this far, then tricky got me in, Thu 11 Jun 2009, 11:08, Reply)

I don't know, but it's a nice idea
"Behold, I write letters with the AWESOME POWER OF METEORITES! ROOOOAAAR!"
*scribble-scribble-scribble*
(LongJohnBaldry, Thu 11 Jun 2009, 11:46, Reply)

Not all of it,
but a lot of it does. There's an anomalously rich layer of it in the earth's crust, which has been found by geologists to coincide with the period when the dinosaurs were wiped out. This is consistent with a globally significant meteorite impact at that time.
( K2k6 has a proper job these days, Thu 11 Jun 2009, 12:13, Reply)