Most of my international e-mail is about sperm whales and giant clams. In those letters, readers rarely ask about the animals. Instead people pose financial and legal questions, about which I know almost nothing.

Besides being big, beautiful and endangered species, sperm whales and giant clams don't seem to have much in common. But these two marine animals share another notable trait. Both occasionally grow tumors that people might, or might not, pay a lot of money for. Those tumors, of course, are ambergris and pearls.

I'm using the term tumor loosely because most tumors are lumps of living cells with no physiological function. The cells in ambergris and pearls, however, are not alive after the animals secrete them, and the resulting masses do have a purpose. Both substances enclose foreign bodies that might otherwise impair the animals' health.

In sperm whales the foreign objects are the hard beaks of squids, the whales' main food source. Usually these sharp mouth parts pass through the whale's digestive tract, but sometimes they accumulate. Then the whale's body produces a material that encases and breaks down the beaks, thus protecting the animal's intestinal lining.

Sperm whales eventually defecate these buoyant masses, and they drift around the open ocean until they wash ashore.

People who find ambergris get excited, some over the prospect of getting rich from it, and some simply from the thrill of finding a natural marine treasure.

One of the latter is a former Honolulu firefighter who found a chunk of ambergris (confirmed by NOAA whale researchers) years ago on a Hawaii beach. He considered this a gift from the sea, and after he read my column about ambergris, he generously cut off a piece and gave it to me. That waxy wedge doesn't look like much to some people, but in my home it's a jewel that holds a place of honor. (Thank you, Roger.)

Speaking of jewels, giant pearls also cause a lot of excitement among people who think the pearls are worth millions.

Giant clams secrete a substance called nacre around foreign bodies that sometimes get through their filtering system. As a clam grows so does its pearl.

Of course, there's a world of differences between natural pearls and ambergris, but one stands above all others: Sperm whales excrete their ambergris, but to get a pearl, you have to kill the clam.

Another distinction is usefulness. Some perfume makers believe that perfume made with ambergris is better than that made with synthetics. The point is arguable, but I leave that to perfume experts.

Where's the sense, though, in coveting enormous misshapen pearls? Spherical perfection is what makes pearls valuable as jewelry. Giant clam pearls look like grubby snowballs made by 2-year-olds. Large size in pearls is also prized, but 14 pounds seems a little heavy for a necklace.

This 14-pounder is the largest pearl ever found (after killing a magnificent clam about 200 years old) and has brought deceit, violence and lawsuits to people who owned it, thought they owned it or wanted to own it. The highest price I've seen for this pearl, which might be wishful thinking, is $75 million.

Maybe ambergris and giant pearls are valuable to certain people and legal to possess, and maybe they aren't. All I know is that I'm not the one to ask.

Ask me about the animals that make them, though, and I'll work hard to find an answer.

Susan Scott can be reached at www.susanscott.net.