Seawater refers to the water that constitutes the oceans and seas, covering more than 70% of the Earth’s surface. It is a complex mixture containing 96.5% water, 2.5% salts, and a small percentage of other substances (dissolved organic and inorganic materials, atmospheric gases, etc.).
Have you ever wondered if seawater is a mineral? In this article, we will answer this question by first discussing what constitutes a mineral. Then, we will look at the properties of seawater and see if it meets the requirements of being a mineral. Finally, we will talk about the various uses of seawater.
Is Seawater Considered a Mineral?
No, seawater is not considered a mineral because it does not meet the other requirements of being a mineral. It is not solid, its chemical composition is not well defined and molecules are not arranged in an orderly fashion.
A mineral is a solid chemical compound with well-defined chemical composition and a specific crystal structure (ordered arrangement of atoms, ions or molecules) that occurs naturally in pure form.
As we will see, despite being naturally occurring, seawater does not meet the other requirements of being a mineral. Its composition varies from place to place, and it also contains organic matter. We will look at these points in greater detail below.
What Qualifies to be Called a Mineral?
As per geology, a substance has to meet the following five requirements to be deemed a mineral:
- Naturally occurring: It must not be manmade but has to exist in the world naturally.
- Inorganic: It should not be alive and must not be made up of plants and animals.
- Solid: It should not be in a liquid (water) or gaseous (air) state.
- Chemical Composition: It should be made up of a particular mix of chemical elements.
- Atomic Structure: The chemical elements should be arranged in a definite way.
This definition of minerals does not include compounds occurring in living things. But some minerals can be biogenic (products made by living things) like calcite or can be organic compounds in terms of chemistry like mellite.
It is also important to distinguish minerals from rocks and mineraloids. A rock is any solid geologic material that is homogenous at a large scale. A rock can contain one or several minerals within itself. A mineraloid is a natural solid substance that does not have a definite crystalline structure. For example, obsidian and opal.
Why is Seawater Not a Mineral?
Sea water is not a mineral because it does not meet all the requirements that we have mentioned above.
Yes, seawater does occur naturally on Earth and covers a significant portion of it. But this is the only requirement that seawater meets completely.
No, seawater is not completely organic. As we discussed above, seawater is constituted of a lot of things, including dissolved inorganic and organic materials.
But seawater also includes dissolved organic substances. These include carbohydrates, amino acids, and organic-rich particulates. These exist in the upper 100 metres of the ocean, where photosynthesis transforms dissolved inorganic carbon into organic matter.
No, seawater is liquid. Of course, it can get transformed into a solid (ice) or gaseous (vapors) state. But because sea water does not meet the other requirements, this does not matter much.
But this leads to a more interesting question. Is ice a mineral? Yes, ice meets all the mentioned requirements but only requires some qualification for the first. A mineral has to be naturally occurring, and while ice does exist on its own, it can also be created through human action.
So, we can say that when it exists naturally (like a snowflake), ice is a mineral. But when it is produced by human action (such as in a refrigerator), then it’s not a mineral.
4. Chemical Composition
No, seawater does not have a fixed and consistent chemical composition. This is because it is influenced by a variety of chemical transport mechanisms.
At some places, say near a deposit of a mineral, seawater is going to have a much larger amount of that mineral than at other places. The salt content of seawater also varies, being lower near the equator and both the poles.
Compare this to a common mineral like Silver. No matter where you take silver, its chemical composition will always be the same. We can think of seawater as a mixture, whose composition always varies depending on the constituting elements.
5. Atomic Structure
No, the molecules of seawater are not arranged in an orderly fashion. It is a liquid with no definite structure.
In its solid state as ice, we might say that it has a definite arrangement. But even then, since its constituting elements would contain different amounts of organic and inorganic elements, its final arrangement is unlikely to be consistent.
As we discussed above, because seawater is made up of such a large mix of elements, it’s hard to argue that it can have a definite atomic structure.
Earlier, we saw that ice (at least when it occurs naturally) is considered a mineral. But what about water? Some argue that although water does not qualify in its liquid state, it does transform into a mineral as ice and should therefore be called a “mineraloid”—a solid that only lacks a definite crystalline structure.
One final thought for this subtopic. You must have surely heard of the term “mineral water”. What exactly does it mean? Well, that is something slightly different from what we have been discussing.
Mineral water is water that comes from a mineral spring, containing minerals like salts and sulfur compounds. In general use, it refers to bottled carbonated water, as opposed to tap water. So, the term doesn’t have to do with whether water is a mineral or not.
Composition and Properties of Seawater
As discussed in the beginning, seawater is made up of water, salts, dissolved organic & inorganic compounds, and atmospheric gases. Seawater on average has a salinity of 3.5%, meaning that every kilogram (one litre in volume) of seawater has about 35 grams of dissolved salts (mostly sodium and chloride ions).
Inorganic carbon, boron, and fluoride constitute the majority of dissolved substances in seawater. Inorganic phosphorous and nitrogen are also present in minor amounts, and they are important for the growth of organisms in the sea. Besides these, there are also several organic elements like carbohydrates and amino acids.
The properties of seawater are quite similar to that of fresh water. Like fresh water, seawater also favors the formation of bonds among molecules. The salt content of seawater plays a key role in shaping its properties:
- Because of its higher salinity, the viscosity (a measure of resistance to deformation) of seawater is higher than salt water.
- The same goes for its density, which is why it’s easier to swim in the sea than in a river.
- Seawater’s boiling point is higher than that of fresh water, and its freezing point is lower.
Various Minerals That are Found in Seawater
The most abundant minerals found in seawater are chloride, sodium, magnesium, sulfur, calcium, and potassium. They make up about 99% of the sea salts.
Their percentage in a given amount of seawater varies because the amount of water can increase or decrease locally due to evaporation or rainfall.
Some of the minerals that are found in seawater are: Chloride, Sodium, Magnesium, Sulfur,Calcium, Potassium, Bromine, Carbon(inorganic), Strontium, Boron, Silicon, Carbon (organic), Aluminum, Fluorine, Barium, Iodine, Copper, Arsenic, Iron, Uranium, Zinc, etc.
You can check out this page on Standford’s website to find out the detailed mineral makeup of seawater.
Various Uses of Seawater
There are several uses of seawater:
- Potential for Health Benefits: Research shows that deep sea water is rich in nutrients like magnesium, calcium, potassium etc. because of which seawater has the potential to be a source of health. It can help especially tackle lifestyle-associated diseases like diabetes, cardiovascular diseases, etc.
- Biological Balance: While we think of the atmosphere as the main reservoir of gases like carbon dioxide and oxygen, the oceans are an even larger storehouse. They produce half of the planet’s oxygen and store about 50 times the carbon dioxide in the atmosphere. This is essential for maintaining the biological balance of Earth.
- Trading: Seawater provides an essential means of transportation, which facilitates the global trade industry. Maritime transport accounts for 80% of international trade.
- Electricity: The oceans are in constant movement through waves, tides, and currents. These movements have different causes: winds result in waves; tides are due to the moon and the sun; currents are caused by differences in water temperature and rotation of Earth. These movements of the ocean can be used to produce clean and renewable electricity.
- Use After Desalination: Through desalination or osmosis, the salt content of seawater can be removed, making it usable for human activities. Currently, the process is expensive and is therefore only performed on a large, industrial scale. But perhaps, in the future, the desalination of seawater will finally solve the water crisis.
In this article, we have discussed whether seawater can be considered a mineral or not. We began by looking at the definition of a mineral, which must necessarily have five features; it should be natural, solid, inorganic, and have a definite chemical composition and atomic arrangement.
Then, on comparing seawater’s features, we found out that it does not satisfy these requirements fully and is therefore not a mineral. Then we discussed the composition, properties and the various kinds of minerals found in seawater. Finally, we looked at some of the uses of seawater.