Hello and thanks for the query.
These calcium deposits are called as heel spur.
heel spurs are an abnormal type of bone growth that extends from the heel bone, particularly on the bottom front of the heel bone and sometimes slightly to the side. Usually, a heel spurs forms where the plantar fascia ligament attaches to the bottom of the heel bone. The heel spur growth is made up of calcium deposits that form when the plantar fascia pulls away from the heel. 

There can be many causes of heel spurs. Most often, athletes or those who have active lifestyles are particularly prone. This is because regular running, jumping, or any activity that can cause the plantar fascia ligament to stretch or extent excessively can cause a heel spur to develop. Those who also lift heavy objects regularly can also cause too much strain to be placed on the fascia, causing it to pull away from the heel bone. The body's response to this process is depositing calcium in the area of the front bottom portion of the heel, resulting in the bony heel spur. 

The Heel Spur growth itself has no feeling. However, pain results from the protrusion of the Heel Spur into soft tissue around the heel of the foot. The area around the spur may become inflamed and cause pain, as well as bruising, as the pointed spur digs through sensitive nerves and tissue. Pain is particularly painful when standing or walking on the inflamed area. Following periods of rest, such as getting out of bed in the morning, pain can be most severe since the heel spur is digging into tissue for the first time after weight has been taken off of the injured heel. 

There are many heel spur treatments to choose from, however there are very few that are effective in reversing the cause of heel spurs. Treatments advised are
1
Lose weight if your are overweight. Excess poundage puts extra pressure on the heels.
2
Throw away your high heels, or at the least, wear heels sparingly. Heel spurs are much more common in women than in men because of the sytle of ladies' footwear. High heels cause excessive stretching of the heel ligament, and increase stress and trauma to the arch and heel.
3
Wear shoes with good motion control to help stabilize the heel.
4
Stretch before exercising. Gently warm up the ligaments of your feet and legs with slow and easy knee bends, toe curls and rotating the ankles in circles.
5
Add cushioning to the heels of your shoes. Consider adding a heel cradle or cup, available where orthopedic-style shoes are sold.
6 
Apply an ice pack to your heel, if the heel becomes painful and swollen.
7
Ask your doctor about ultrasound, physical therapy and "strapping," to avoid the need for heel spur surgery.
8
See a doctor for an injection of steroid administered near the heel. Steroids can reduce pain, inflammation and swelling.
9
Surgery for Calcium Deposits
Podiatrists generally perform bone spur surgery on an outpatient basis. The surgeon removes the bone spur on the toes by making a small incision on the affected area and filing down the bony outgrowth with a file or power bit. 
I hope to have answered your query however you can revert to me for any other query.
Thanks and best of luck.

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