Calcium buildup looks different depending on where it forms. On the skin, it typically appears as firm, whitish or yellowish bumps or patches. Inside the body, calcium deposits show up as bright white spots on X-rays and CT scans. The appearance varies widely by location, from a cloudy band across the eye to tiny white flecks on a mammogram to chalky lumps under the skin that you can feel with your fingers.
Calcium Deposits on the Skin
When calcium collects in the skin, a condition called calcinosis cutis, it forms firm, whitish or yellowish bumps that sit on or just below the surface. These can range from tiny papules a few millimeters across to larger plaques or nodules. They feel hard to the touch, almost like small pebbles embedded under the skin. In some cases they’re painless and barely noticeable. In others, they become tender over time.
If a deposit breaks through the skin, it releases a chalk-like, creamy white material. This discharge is mostly calcium phosphate with a small amount of calcium carbonate, essentially the same minerals found in bone. The texture is pasty, similar to toothpaste. People with autoimmune conditions like scleroderma or dermatomyositis are more likely to develop these visible skin deposits, though they can also appear at sites of previous injury or surgery.
What It Looks Like in Arteries
Calcium buildup in the coronary arteries isn’t something you can see or feel from the outside. It’s detected through a coronary calcium scan, a specialized CT scan that takes cross-sectional X-ray images of the heart. On these images, calcium deposits appear as bright white spots within the artery walls, standing out sharply against the surrounding tissue.
The calcium is part of a larger buildup called plaque, which also contains fats and other substances. A radiologist measures both the total area and the density of the calcium to generate a score (called an Agatston score). A score of zero means no detectable calcium. Higher scores indicate more extensive deposits and correlate with greater cardiovascular risk. The calcium itself isn’t the whole problem. It’s a marker that plaque has been accumulating in the artery walls over years or decades.
Calcium Flecks on a Mammogram
Breast calcifications are among the most commonly spotted calcium deposits, picked up routinely during mammograms. They appear as small white specks or dots against the darker breast tissue. Their shape, size, and pattern help radiologists determine whether they’re harmless or worth investigating further.
Most breast calcifications are benign. Large, round, clearly defined spots, sometimes described as “popcorn-like,” typically form in aging tissue and are nothing to worry about. Vascular calcifications follow the tracks of blood vessels in neat parallel lines. “Eggshell” calcifications look like thin rings of calcium deposited on the surface of a tiny sphere, usually less than 1 mm thick when viewed from the side. Milk of calcium appears fuzzy and round on one view but crescent-shaped, like a teacup, when the breast is imaged from the side.
The calcifications that draw closer attention tend to be very small (under 0.5 mm), irregular in shape, and clustered in patterns that follow the path of a milk duct. Fine, branching lines of calcium can suggest material filling the inside of a duct. These patterns don’t necessarily mean cancer, but they typically prompt additional imaging or a biopsy to rule it out. Scattered or diffuse calcifications spread across both breasts almost always turn out to be benign.
Calcium in Tendons and Joints
Calcific tendonitis, most common in the shoulder, produces calcium deposits that show up on X-rays as white, cloudy masses within or near the tendon. Their shape varies: about half appear elongated or comet-tail shaped, while others look round or irregular. On average, these deposits measure roughly 2 cm by 1.2 cm, though they can range from as small as 0.5 cm to as large as 4 cm across.
The texture of the deposit also varies by stage. In earlier phases, the calcium tends to look solid and well-defined on imaging. As the body starts trying to reabsorb it, the deposit becomes more stippled or fragmented, appearing as scattered flecks rather than a single mass. This reabsorption phase is actually when the deposit tends to be most painful, even though it’s shrinking. From the outside, you typically can’t see a tendon calcification, but you’ll feel it as sharp pain during certain movements, particularly reaching overhead.
Calcium Buildup in the Eyes
A condition called band keratopathy causes calcium salts to accumulate in the cornea, the clear front surface of the eye. The deposit forms a horizontal, belt-shaped band across the part of the cornea that’s visible when your eyes are open. It starts at the outer edges and gradually moves toward the center.
To other people, it looks like a white-gray, cloudy stripe across the eye. Up close, it may have small clear spots that look like holes within the band. As the deposit thickens, it makes the normally transparent cornea look murky and dull, which can blur vision. During a slit lamp exam (a standard eye examination using a microscope and bright light), the band and its texture become clearly visible. Band keratopathy is associated with chronic eye inflammation, elevated blood calcium, and long-standing eye conditions.
Calcium Deposits in the Brain
Calcium can also accumulate in the brain, particularly in a region called the basal ganglia, which is involved in movement control. These deposits are best detected on a CT scan, where they appear as bright, symmetrical white spots deep within the brain. MRI is actually less reliable for spotting them.
Small, punctate calcifications in this area are surprisingly common, showing up as incidental findings in up to 20% of healthy people on brain CT scans. These tend to be tiny and confined to a specific part of the basal ganglia, and they increase with age. In most cases, they cause no symptoms at all. More extensive calcifications that spread into surrounding brain structures like the thalamus or cerebellum can be associated with neurological symptoms, but the isolated spots found on routine scans are typically harmless.
Why Calcium Builds Up in Different Places
There are two main biological reasons calcium ends up where it shouldn’t. The first, and most common, is called dystrophic calcification. This happens when calcium deposits form in damaged or abnormal tissue, even though your overall calcium levels are perfectly normal. Think of it as calcium settling into tissue that’s been injured by inflammation, surgery, or autoimmune disease. The chemistry at the site of damage mimics what happens during normal bone formation, pulling calcium out of the bloodstream and into the tissue.
The second type, metastatic calcification, works in the opposite direction. Here, the tissues are healthy, but blood calcium or phosphate levels are abnormally high. The excess minerals deposit into otherwise normal organs, including the lungs, heart, and under the skin as diffuse nodules. This pattern is most often seen with chronic kidney disease, which disrupts the body’s ability to regulate calcium and phosphate. It can also occur with certain cancers and other conditions that raise blood calcium.
Regardless of the underlying cause, calcium deposits share a common visual signature: they’re dense, white, and chalky. Whether you’re looking at a lump under the skin, a bright spot on a CT scan, or a cloudy stripe across the eye, you’re seeing the same basic mineral accumulation in a place the body never intended it to be.