Minerals are found in the earth’s crust, in water, in the foods you eat, and stored throughout your own body. They originate in rocks and soil, dissolve into groundwater, get absorbed by plants, and move up the food chain into meat, dairy, and seafood. Understanding where minerals actually come from helps explain why some diets fall short and why the water you drink matters more than you might think.
How Minerals Start in Rocks and Soil
Every mineral your body uses traces back to the earth’s crust. The crust is dominated by silicate minerals: feldspar alone makes up roughly 52% of it, followed by quartz at 12%, pyroxenes at 11%, and micas, amphiboles, and clay minerals at about 5% each. These geological minerals aren’t the same as “dietary minerals,” but they’re the original source. Calcium, potassium, magnesium, iron, zinc, and dozens of other elements are locked inside these rock structures.
Weathering breaks rocks down over thousands of years. Rain, temperature swings, and chemical reactions dissolve minerals out of rock and into soil and groundwater. Sand and silt particles in soil come directly from parent rocks, while secondary mineral compounds form through chemical changes within the soil itself. Plants then pull these dissolved minerals up through their roots, converting geological minerals into the forms your body can use.
Minerals in Plant Foods
Plants are the primary bridge between minerals in the ground and minerals on your plate. As roots draw water from the soil, dissolved mineral ions come along for the ride and get incorporated into the plant’s tissues. This is why soil quality directly affects the nutritional value of produce.
Different plant foods concentrate different minerals:
- Magnesium: Nuts, seeds, legumes, leafy green vegetables, and chocolate. Magnesium plays roles in bone structure, muscle contraction, and immune function.
- Potassium: Fresh fruits, vegetables, whole grains, and legumes. Your body uses potassium to maintain fluid balance and transmit nerve signals.
- Manganese: Widespread in plant foods generally, supporting enzyme activity throughout the body.
- Iron: Leafy greens, legumes, and fortified grains contain non-heme iron, which your body absorbs less efficiently than the iron found in animal products.
One concern with plant-sourced minerals is that modern farming may be reducing what’s available in the soil. A Penn State study analyzing 430 rivers across the U.S. found that phosphorus loss from agricultural lands has increased over the past four decades, despite efforts to reduce it. When key nutrients wash away from farmland, crop yields and nutritional density can both decline.
Minerals in Meat, Dairy, and Eggs
Animal products concentrate minerals that animals themselves absorbed from plants and water during their lifetimes. This makes meat, dairy, and seafood particularly rich sources of certain minerals that are harder to get from plants alone.
Dairy is one of the most concentrated food sources of calcium. A single cup of skim milk provides about 302 mg of calcium, whole milk delivers 291 mg, and one ounce of cheddar cheese contains 202 mg. By comparison, most non-dairy foods provide far less per serving.
Red meat is a strong source of both iron and zinc. A 3-ounce serving of braised lamb contains 4.3 mg of iron, braised pork shoulder provides 3.5 mg, and broiled sirloin steak delivers 2.4 mg. Poultry contains less: roasted chicken has about 1.3 mg per serving, and turkey just 0.9 mg. The iron in animal products is heme iron, a form your body absorbs two to three times more efficiently than the iron found in plants. Zinc is found in especially high concentrations in meat, poultry, shellfish, eggs, and fish.
Minerals From the Ocean
Seawater is essentially a mineral solution. It contains sodium, magnesium, calcium, potassium, chloride, selenium, and iodine, among other elements. Deep sea water tends to have different mineral concentrations than surface water. One striking example: iodine levels in deep sea water can reach 5.5 mg/L, compared to just 0.064 mg/L at the surface.
Seafood absorbs these ocean minerals directly. Shellfish like clams, scallops, and oysters are well known for their zinc and iron content. Canned salmon provides some calcium (about 17 mg per 3-ounce serving), especially when you eat the soft bones. Seaweed and kelp are among the richest natural sources of iodine, a mineral that’s difficult to get from land-based foods without iodized salt.
Minerals in Your Drinking Water
Water picks up minerals as it filters through rock and soil, which means your tap water contains varying amounts of calcium and magnesium depending on where you live. This is what people mean by “hard” water versus “soft” water.
North American tap water from surface sources contains anywhere from 2 to 83 mg/L of calcium and up to 29 mg/L of magnesium. Groundwater sources tend to run higher, with calcium ranging from 26 to 85 mg/L and magnesium from 2 to 48 mg/L. Bottled mineral waters vary even more dramatically. North American brands range from 3 to 310 mg/L of calcium, while some European mineral waters reach as high as 575 mg/L of calcium per liter.
For people who drink several liters of water daily, these numbers add up. Hard tap water or mineral-rich bottled water can meaningfully contribute to your calcium and magnesium intake, while soft water or heavily filtered water provides almost none.
Where Your Body Stores Minerals
Once you consume minerals, your body doesn’t just use them and discard them. It stockpiles them in specific tissues for ongoing access.
Your skeleton is the largest mineral storage site. Bones are a living matrix of protein reinforced with hydroxyapatite crystals, a calcium-rich mineral compound that gives bones their hardness and structural strength. Your teeth are even more mineral-dense. Tooth enamel is 96% mineral, making it the hardest tissue in your body. The hydroxyapatite crystals in enamel are roughly 1,000 times larger than those found in bone.
Iron is stored primarily in red blood cells (as part of hemoglobin, the molecule that carries oxygen) and in your liver. Zinc concentrates in muscle tissue, bones, and skin. Potassium stays mostly inside your cells, where it helps regulate fluid balance and electrical signaling. Your body carefully manages these mineral reserves, pulling from storage when dietary intake drops and replenishing when you eat mineral-rich foods. This buffering system means that short-term gaps in your diet rarely cause immediate problems, but long-term deficiencies gradually deplete these reserves and lead to noticeable symptoms like fatigue, muscle cramps, or weakened bones.