When iridium grains first appeared in fountain pens, they were indeed made of natural metal iridium balls, which contained iridium and osmium. But in the more than 100 years of the evolution of the pen, iridium particles have undergone changes from natural to artificial, from two metals to alloys. For most of the 20th century, iridium particles were made of platinum group metals, but the metals osmium and ruthenium were later found to produce highly toxic and volatile tetraoxides at high temperatures in contact with oxygen. Environmental protection needs to be removed. Now the iridium particles of major pen factories are kept as commercial secrets, and it is not easy to obtain.

However, we can obtain some information from a small amount of domestic iridium particles. In the early days of the founding of the People's Republic of China, iridium particles were still obtained by pure imports. Later, some pen factories tried to extract platinum group metal iridium particles from scrap metal scraps for polishing nibs. success. Later, domestic equipment and technology gradually developed, and in the late 1950s, iridium pellets were successfully made. Later, different kinds of iridium particles such as 601, 617, 412, 188, 823 were melted with different formulas. 601, 412 and other iridium grains are used in gold pens, mostly iridium or ruthenium-based alloys, while 188 iridium grains are iridium grains made for steel-pointed pens, which do not contain platinum group metals, and may be composed of tungsten, chromium, etc. , is cheaper.