Casting Spellword is: Grainicus Barium

But can someone make a ranged attack through it?

And does it block a portion of an area effect spell?

Quote from WeTheAwesome >>

But can someone make a ranged attack through it?

And does it block a portion of an area effect spell?

 Someone making a ranged attack through it would have disadvantage if they didn't have a way to see through the wall since it blocks line of sight.
It doesn't specify that it blocks spell effects in the area so you should be fine as long as targeting doesn't rely on sight. 
Honestly it's not great for covering your own party but you could target a group of enemy archers and force them to re-position, and moving costs 3 times as much in the wall so it would take 30 ft to cross the area, potentially giving your party time to deal with them.

You get a 30-foot wide, 10-foot deep wall of swirling sand that costs 3 feet of movement for every 1 foot through the way. In other words, most creatures will spend their entire movement just to get past it. (And then you can push them back in! If they end their turn in the wall, they are blinded - no save.) Great when you need a buffer against a large group of enemies.

Does fire turn a section into glass?

Does Earth Genasi - Earth Walk, work with this? Also a Rogue could hide in the sand as "blocks vision" is heavily obscured

RAW, Earth Walk would have no affect on this. It specifies "you can move across difficult terrain made of earth or stone without expending extra movement", and unfortunately nowhere does wall of sand mention difficult terrain. Yes, it is an area that is harder to move through, but without using the term "difficult terrain", it's not difficult terrain RAW. Whether a DM would be up for allowing Earth Walk to bypass this is a different matter. 

As far as I can see, there's a few spells that cost extra movement in a similar manner, and none of them specify the area is difficult terrain, so I think it's definitely a design choice to have areas that are tougher to move through, but override a character's ability to ignore difficult terrain. Control winds, transmute rock, and wall of thorns are some other examples I found.

Interestingly, the effects of such spells would stack if they overlap and maybe more interestingly, the freedom of movement spell would not prevent you from being affected either, as none of the spells actually reduce your speed, they just cause each foot of movement to cost extra.

thanks for the response!

no but cool homebrew, run it like wall of water and ice damage

Why this isn't part of the Desert Druid additional spells kit, I'll never understand. Heck, nature domain clerics would get a huge kick out of this, too. Why do Wizards get to hog this obscure spell so packed with flavor for other classes?