I'd say no, not while it's mixed with the water. At the very minimum, I'd consider the Size based on the water size, not on the salt size. (At least, I've always assumed that to target a Part of a giant, you need extra magnitudes over the base Corpus Individual, even if said Part is small).
As for how much salt you can get out of water, it's relatively easy. Very roughly, for every 30 weight units of sea water you get one weight unit of salt. But salt is roughly twice as heavy as water, so you need roughly 60 cubic paces of sea water to get one cubic pace of salt. Base Individual for water is a pool 5 paces across and two paces deep. It's not clear if it's circular, in which case it's slightly less than 40 cubic paces, or square, in which case it's 50 cubic paces. All told, a Base Ind of water holds a little less than a cubic pace of salt (about 2/3rds to 5/6ths), let's say about 1 ton of salt.
I think I consume about 1Kg of salt/year, and random internet sources say that was a "family"'s yearly consumption in the middle ages; so let's say 1Kg of salt was what a well-off person or a poor family consumed. A salt miner was able to mine 1000 times that, i.e. 1 ton i.e. the salt from 1 Base Ind of water. I'd say the production of miner is worth 1 Mythic Pound, from how much unskilled labor is worth in covenants. Another way to find the worth of 1Kg of salt, is that in 15th century london it was worth about a half a penny, i.e. a ton would be worth about 2 pounds of silver -- but there was a significant increase in prices in from 1220, plus taxes etc., so I guess 1 MP for 1 ton is about right.
So, once again. A base Ind of Aquam yields about 1 ton of salt, worth about 1 Mythic Pound, and enough salt for 1000 rich people or 1000 poor families. To ensure a Typical source of income (100MP/year), you could in theory just go to the seaside for a day every year with a couple of grogs, dig a largish hole on the beach (about 120 cubic paces, say 2x8x8), and while standing in the sea cast a ReAq5 (Base 4,+1 Touch) spell to bring into the hole a Base Ind of sea-water, and ReAq5 (Base 3,+2 Voice) spell to evaporate the water and leave the salt, repeating the process 100 times. With a decent Rego Aquam total you can probably handle that as a non-fatiguing spontaneous spell, the entire process takes less than half an hour (300 rounds) plus the time to dig the hole (a few grog hours while you take your sun tan!). Assuming salt counts as sand for the purposes of Terram, what you get is about 7-8 base Individuals of Terram. It would take a simple ReTe 10 spell (Base 3, +1 Touch, +1Conc, +1Siz) to move the stuff.
Then, you'd need to sell it over a year. To guarantee your Typical (100MP) source of income, your customer base needs to be one hundred thousand well-off people (or poor families) who get all their salt from you. That's the population of a pretty large area! I guess your main problem with salt is not producing it, but selling it while dealing with all the taxes, monopolies etc. -- and not disrupting the existing mundane market too much