The Von Kossa technique yields black deposits as a result of silver impregnation indicating the presence of which element?

• A. Calcium
• B. Iron
• C. Copper
• D. Magnesium

Answer: (A)

The Von Kossa technique visualizes mineralized tissue by silver impregnation, turning areas that contain calcium salts black. The silver nitrate treatment causes silver to deposit as silver phosphate or silver carbonate in regions where phosphate or carbonate ions are present—these ions are part of the mineral phase (calcium phosphate and related minerals) in bone and other calcified tissues. So the black deposits indicate the presence of calcium salts in the tissue. This method does not indicate iron, copper, or magnesium in the same way.