A crystal is any solid that has an organized structure. ... So it is a prerequisite to be a crystal in order to be a mineral. All minerals, therefore, form crystals. On the other hand, there are crystals that are not minerals, because they are not naturally occuring, or because they are not inorganic
Source: http://www.geologyin.com/2016/03/what-is-difference-between-minerals-and.html?m=1
Answer is: <span>concentration of fluoride in the water in parts-per-million is 1 ppm.
</span>Parts-per-million (10⁻⁶) is<span> present at one-millionth of a </span>gram per gram of sample solution, f<span>or example mg/kg.
</span>m(fluoride) = 500 g · 1000 mg/g = 500000 mg.
m(water) = d(water) · V(water).
m(water) = 1 kg/L · 500000 L.
m(water) = 500000 kg.
arts-per-million = 500000 mg ÷ 500000 kg = 1 mg/kg = 1 ppm.
