Which mineral precipitates from oceans and forms rock salt? 1 quartz 2. fluorite 3 halite olivine
The Correct Answer and Explanation is:
The correct answer is: 3. Halite
Explanation
Halite, commonly known as rock salt, is the mineral that precipitates from oceans and forms rock salt deposits. It is composed primarily of sodium chloride (NaCl) and forms through the process of evaporation. When seawater or saline water bodies evaporate in hot, arid environments, dissolved minerals begin to crystallize out of the solution. Halite is one of the first minerals to precipitate once the water becomes supersaturated with sodium and chloride ions.
This process typically occurs in evaporitic environments such as salt flats, playas, or enclosed shallow basins where water inflow is limited, and evaporation rates are high. Over time, large beds of halite can accumulate and become buried, eventually lithifying into rock salt.
Halite is distinct in its physical properties. It usually forms cubic crystals, is colorless to white (though it can appear in other colors due to impurities), and has a salty taste. It is also relatively soft, rating only 2.5 on the Mohs hardness scale, and it dissolves easily in water.
In contrast, the other minerals listed—quartz, fluorite, and olivine—do not typically form from evaporating seawater:
- Quartz (SiO₂) forms from silica-rich solutions and is highly resistant to weathering.
- Fluorite (CaF₂) forms in hydrothermal veins and hot springs but not commonly through marine evaporation.
- Olivine is a silicate mineral that forms in igneous rocks such as basalt and peridotite, deep within the Earth’s mantle or crust.
Thus, halite is the correct answer because it directly precipitates from evaporating seawater and is the primary component of rock salt, a major evaporite mineral.
