First, I apologize for the cardinal sin of equating real life to fantasy.
With that out of the way, does Glaucite make sense in that it's used as the premier metal for building spaceships?
A quick google search tells me that the ideal metal for spacecrafts is aluminum for being both sturdy and light.
Glaucite is stated to be 50% heavier than steel which is already quite a few bags of feathers.
Is the hidden caveat that Glaucite is only made for ships that are never meant to take off from a planet?
My Iron Gods campaign took a strange twist in The Divinity Drive. The five party members, one an amazing technological crafter, one a good technological crafter, one a good magical crafter, and two who were excellent mundane crafters, persuaded Unity to hire them as repair crew. Therefore, I had to find repair jobs for them.
One repair job was fixing a 30-foot wide hole in the hull of the starship Divinity. I invented convenient properties for glaucite. I made technological devices called a glaucite cutter, which could easily cut glaucite, a glaucite shaper, which could bend glaucite, and a glaucite fuser, which could heatlessly weld together glaucite. The repair crew was able to seal up the hole with the reserve glaucite stock set aside for repairs. Repairing a hole like that in a steel or aluminum hull would have required putting the starship in drydock. I could have invented a cutter, shaper, and fuser for aluminum (though as far as I know, Golarion has no aluminum), but since that is a real metal, those devices would be less believeable.
Thus, in my private interpretation, glaucite was used for spaceship hulls because holes could be quickly repaired in space.
The real reason behind glaucite is that Paizo wanted to point out that aliens had access to exotic metals: abysium, adamantine, djezer, horacalcum, inubrix, noqual, and siccatite. The cheapest of these, adamantine, is too valuable to leave pieces lying around, so they created an alloy of iron and adamanite that was cheap enough to leave lying around. My players learned to smelt the adamantine out of glaucite with a nuclear plasma beam, so I had to establish that glaucite was 99% iron, becauce otherwise they got too much adamantine out of the smelting.
The real reason behind glaucite is that Paizo wanted to point out that aliens had access to exotic metals: abysium, adamantine, djezer, horacalcum, inubrix, noqual, and siccatite. The cheapest of these, adamantine, is too valuable to leave pieces lying around, so they created an alloy of iron and adamanite that was cheap enough to leave lying around. My players learned to smelt the adamantine out of glaucite with a nuclear plasma beam, so I had to establish that glaucite was 99% iron, becauce otherwise they got too much adamantine out of the smelting.
But, why make it heavy?
The real reason behind glaucite is that Paizo wanted to point out that aliens had access to exotic metals: abysium, adamantine, djezer, horacalcum, inubrix, noqual, and siccatite. The cheapest of these, adamantine, is too valuable to leave pieces lying around, so they created an alloy of iron and adamanite that was cheap enough to leave lying around. My players learned to smelt the adamantine out of glaucite with a nuclear plasma beam, so I had to establish that glaucite was 99% iron, becauce otherwise they got too much adamantine out of the smelting.But, why make it heavy?
Adamantine has hardness 20, so the developers gave glaucite hardness 15 to increase the association with adamantine. That made it a superior metal, so they had to give it serious disadvantages to prevent a glaucite export industry spreading glaucite outside Numeria. Hardness, price, weight, hit points per inch, resistance effects, and magical effects are the properties of metal in Pathfinder. They made the price high, thrice the price of iron, which made sense. They made the weight high, 50% heavier than iron, which does not make sense.
Weird magnetic effects giving a -1 penalty to Dexterity rolls while wearing glaucite armor or shield would have been a better choice than 50% more weight.