A great museum, like a stuffed gorilla, can be huge and interesting yet not very useful.

The gems and minerals section of the Smithsonian's Museum of Natural History, for instance, is full of fabulous crystals and gee-whiz gems, but it doesn't tell you much about rocks, even the ones called gems and minerals. Most modern museum displays seem designed simply to dazzle; few of them offer enough information to flesh out a grade-school science project.

The visitor who wants to go deeper into a subject, or who has an artifact or odd rock he wants to know more about, will usually be disappointed. Generally only university-accredited researchers are admitted to the inner sanctums where the heavy stuff is.

The Smithsonian has made a conspicuous exception to that policy by creating The Naturalist Center, designed to open the resources of the Natural History Museum to the more-than-casual visitor. Staffed by friendly and knowledgeable volunteers, the center offers hands-on specimens and equipment, small but excellent libraries and -- for worthwhile inquiries -- access to the institution's hundreds of specialists.

While it operates more or less on a shoe-string, the center has impressive resources, including a collection of 10,000 microscope-mounted mineral specimens, a multitude of insects and shells, and plenty of icky things preserved in jars.

"What we are trying to build is a solid general collection in six major disciplines [minerals, plants, invertebrates, insects, vertebrates and anthropology] with special emphasis on the Middle Atlantic region," said acting manager Garry Groupe.

"Most of our visitors are either young people doing research or local residents who have found something they can't identify from library references or general guide-books.Whatever brings them in, the ones who keep coming back often work their way through all six areas, because they find it interesting. Then we make docents of them."

It takes a lot of people to keep the exhibits in order and help visitors during the public hours, which run Wednesday through Sunday. Not being able to manage a seven-day schedule, the center staff chose to work weekends because that's when most visitors are able to come. Generally, admission is limited to children 12 and up, but Exceptions are made for exceptional youngsters.

Although the exhibit sections are logically and simply arranged, pursuing what seems to be a simple question can take a lot of time and assistance. Groupe and docent Suzanne DeBlois, 20, spent something like two hours helping me and my daughters Karen and Laura track down a bat, two Potomac River shells and a question.

The bat, which had been kept in our freezer since it self-destructed on a cartop canoe near Luray, turned out to be a red bat (Lasirius borealis), which should have been obvious but wasn't because the center's stuffed specimen was much the worse for wear. Unless donated by outsiders, the specimens are hand-me-downs from the research departments. Now they have ours.

The shells, snails taken from the riprap at Gravelly Point and mussels from Fort Foote, did not match any in the drawers. They were tentatively identified as Goniobasis lea and M. margaritifera linne. They, too, now rest in the museum and may, once the identifications are verified, go on display. (The center sucks in specimens like a vacuum cleaner, using an irresistible pitch: "Since you found this to be interesting, don't you think it would be a good thing to make it available to others?")

My question was, why do the baldfaced hornets Vespula maculata abandon in the fall those elaborate papier-mache nests they spend the summer building in my eaves? The nests would be nice warm places for the fertilized queens to winter over. Instead, they go and hide under rocks or something, throwing away a dwelling that represents the lifetime labors of hundreds of workers and one that would seem to offer a considerable evolutionary advantage. I learned some fascinating things about wasps (many of them make first-class honey, for instance), but I still don't know why they abandon those nests.