Dolomite. You know the name because these are those mountains in Yugoslavia. . . .

You may also know the name because there are those little pills a lot of people, especially women, are taking as a food supplement, as a muscle relaxant, as an ease to menstrual cramps, as a heart regulator, as a preventive against the fragile bones of aging . . .

It's no coincidence that the mountians and the pills have the same name. Chances are the pills came from them. It's the stuff the mountains are made of: also known as, well, rock.

The kind of rock that is called dolomite is a combination of calcium and magnesium in proportions which happen to -- more or less -- match the proportions of recommended daily allowances for those two minerals: two parts calcium to one part magnesium. (The calcium RDA for women is 800 mg. a day; magnesium, 300.)

Dolomite -- the mineral, calcium carbonate and magnesium -- is closely related to limestone and chalk, even marble. It is believed to be the mineral residue of sea animals of 20 or 30 million years ago, when most of the earth's surface was ocean.

It is probably the principal source of water hardness, so it has crept into the human diet for probably as long as man has existed.

Now, as a food supplement, dolomite has gained a loyal following among health-food afficiandados and, more recently, from some women's health groups.

Writes Barbara Seaman in the book she co-authored with her then husband Dr. Gideon Seaman, The Doctor's Case Against the Pill: "Calcium deficiency is associated with a host of prematrual and menstrual symptoms, including muscle cramps, water retention, headache and nervous symptoms . . ."

Dolomite also has been recommended by non-medical health sources as useful for post-menopausal women who elect against estrogen therapy. Although the estrogen clearly protects the de-calcified bone condition called osteoporosis (a major cause of bone fractures among the elderly, especially white women), it has been linked to various cancers after many years of use.

There is no evidence that additional calcium and magnesium (and vitamin D) will prevent osteoporosis, but there's no evidence that it won't. And since it is a condition involving calcium deficiency, many women have been turning to dolomite.

"There is tentative new evidence," writes Barbara Seaman, "that it is not advisable to take large quantities of dolomite over long periods of time.

Calcium alone, or calcium with magnesium may be more digestible." And as she noted last week, "For some five or six years there has been a concern in the women's movement about contamination with lead."

A Florida doctor also is concerned about lead contamination, as well as other potentially poisonous substances (like arsenic) in dolomite. Dr. H. J. Roberts, in a letter published in the Feb. 12 issue of the New England Journal of Medicine, said he had found that some patients with "neurologic and other disorders" had been "taking considerable amounts of dolomite."

As a result of the Roberts letter, dolomite distributors, the research department of Prevention Magazine and the Food and Drug Administration are checking for toxic contaminants in dolomite prepared for human consumption.

Early indications suggest that there are probably traces of toxic substances in most of the preparations, but not beyond normally acceptable limits.

And what is a "normally acceptable limit?"

Richard Jacobs, acting head of FDA's Nutrient Toxicity Section, says that at "acceptable" levels of lead, for example, "the average person is usually safe. It's the outlying 5 percent which may be at risk. We have a problem because we don't know what or how much people take. Most nutrients, including vitamins, are toxic at some levels."

"Safe and adequate levels," are not the same as "upper limits," which are often unknown.

So far as dolomite is concerned, Jacobs says, "We worry about small operations, like people who might go out to the local mountain and scoop up steam-shovels full . . . who knows what else they scoop up with the dolomite."

Whether or not dolomite in general turns out to be seriously contaminated -- and preliminary tests indicate it probably will not -- the situtation illustrates an increasingly common problem as non-traditional health food programs flourish: Quality control is outside most regulation; benefits are uncertain at best; overdoes or toxic or allergic reactions may go unrecognized, and contamination of some items (like herbal teas) may occur anywhere from point of origin to uncovered bins in health stores.

In fact, it may be true that the benefits of some healthfood substances would be proven if anybody would ever test them.

Meanwhile, however, the benefits of taking indiscriminate quantities of any supplements are dubious. Balances and interactions of many of these substances are physiologically complex, and differ so much from person to person, that there is always the possibility of disorienting any number of delicate biochemical functions.