Hemosiderin is yellowish or brownish in color, amorphous, contains iron, and is insoluble in water, alkalis, alcohol, ether, xylol, and chloroform.

On the addition of potassium ferrocyanid and weak hydrochloric acid it turns blue (Prussian blue reaction).

It occurs in the blood, in cells and intercellular tissues, as a consequence of recent hemorrhages; apparently results from the slow destruction of the erythrocytes.

The granules are taken up by the phagocytes and may be finally removed by them. Cells filled with the granules are frequently found in the sputum in cases of chronic congestion of the lungs.