Kim Byrd, age 10, of Gastonia, North Carolina, for her question:

Is there a metallic element called lutetium?

Yes, there is a metal called lutetium and it is one of the earth's chemical ele¬ments. But you would never find a nugget of lutetium, even if you dug up the ground from coast to coast. It tends to hide, and we always find it mixed with several other elements of the same family.

We can recognize iron and lead, gold and silver because they show their faces in objects we use every day. But many other metals work behind the scenes. We do not recognize them, and some of them have odd sounding names. For example, the metal ytterbium was discovered in the last century and named for a place in Sweden. The atoms in an element, of course, are all alike. Chemists of the day thought that their ytterbium was an element    element number 70 because the nucleus of its basic atom contained 70 proton particles.

Then in 1907, a French chemist named Georges Urbain proved that samples of ytterbium contained two different atoms. Some were element number 70. Others were atoms of the atomic element 71. Urbain was the first to separate the original ytterbiur 4 into two different elements. Element number 70 kept its old name ytterbium. Urbain borrowed Lutetia, an ancient name for the city of Paris, and named element number 71 lutetium.

Lutetium is not one of the common elements we see every day. True, it is one of the 90 or so chemical elements in the earth's crust, but you might dig and delve for miles and miles without finding any of it. And you would not find it all by itself in neat little metal nuggets. Atoms of lutetium are found mixed with atoms of ytterbium, lanthanum and other elements of the so called rare earth family. The atoms of this family are so very much alike that separating them is difficult and expensive.

But nature's mixture of these metals is very useful. It is called misch metal. It is added in small amounts to make fine textured alloys of steel and is used in certain glass making recipes. Different proportions of misch metal create brilliant, colorless glass or glass that is richly tinted with color. Small amounts of misch metal are mixed with iron to make gritty lighter flints. A few atoms in this material may be lutetium. Scientists have learned a lot about other elements of the rare earth family and found many uses for them. But at present, we do not know a great deal about the properties of lutetium and how it can be useful.

Lutetium and its relatives were named the rare earths before scientists discovered that the pure elements were all silverish gray metals. They are not earthy and most of them are not rare. They occur in old fire formed rocks, several of them mixed to¬gether. Lutetium is the heaviest of them and one of the hardest to separate. A pound of lutetium is worth $1,300, but few people would have a reason for buying any.