What is the most abundant mineral in seawater?

Answer 1

That rather depends on what you mean by a mineral. It's a rather vague term and not one which would be used by a chemist. If you mean what elements are present, then hydrogen, part of the water itself is the answer. If you mean the substances dissolved in the water, then chlorine is the most abundant element in those. If you are thinking of compounds, such as salt, then simplistically it's sodium chloride, though all the ions of the dissolved substances float around freely and its a moot point which is associated with which. That's why we often just list the ions present in order of abundance. Chloride ions are the most abundant, and a fuller list is in the link.http://www.lenntech.com/composition-seawater.htm