I'm the kind of person for whom a beach vacation is not complete unless I've scored a piece of sea glass, one of those shards of broken bottle that have been tumbled by water, sand and time into a state of smoothness that renders them treasure.

But a beach full of the stuff? Somehow, despite the fact that I'd been visiting in-laws in Hawaii for 16 years -- spending more time eating, shopping or watching my kids windmill off surfboards than collecting bits of old Vicks jars -- the existence of Kauai's appropriately named Glass Beach had escaped me. Until recently, that is.

Even learning from locals that the beach had been picked over, that there were days you could show up and find nothing but pieces so small they were almost sand, didn't dampen its allure. On my family's next Pacific fling, I resolved, we would take the girls to Kauai.

And somewhere between visits to its majestic canyons, cute towns, idyllic bays and crowded pools, we would find time for my sea glass obsession. Even if the payoff was likely to be minuscule.

Sea glass was once mostly ignored as trash, although, according to Richard LaMotte, author of the collectors' bible "Pure Sea Glass," it at one time may have served as a status symbol in Philadelphia, where residents would place a jar of it in their front windows to illustrate their affluence. Now people collect it, sell it and make things out of it -- from fine jewelry to sun catchers, frames and mosaics, even stained-glass windows.

Part of its newfound appeal is its increasing scarcity. Glass bottles and containers have given way to plastic, shipwrecks have become more rare and people have stopped dumping trash in the oceans, all of which means there is less raw material for sea glass. Further compounding the problem, says LaMotte, one of the founders of the North American Sea Glass Association, is the fact that much of the sand brought in to replenish beaches buries whatever glass is on the shore.

I've certainly never had much luck finding sea glass in Hawaii. The kids and I once collected a cupful on Oahu, but it was mostly pedestrian browns and greens, the color of beer bottles, which makes sense when you consider it: Body surfers, beer and rough waters would conspire to toss back that kind of common stuff. (LaMotte says it can take 10 to 30 years to create sea glass, depending on the "wave action.")

I had higher hopes for Glass Beach, but first we had to find it.

Glass Beach isn't mentioned in most guidebooks, and there are no signs directing drivers to it. The beach turned out to be in the middle of an industrial zone not far from the popular tourist area of Poipu on Kauai's southern end. To get there, you take the Port Allen exit off the highway, then turn down a street past some warehouses, then follow a very rutted dirt road to the water, wondering if you're going to owe money to the rental car company.

You won't know whether you've gone the right way until you walk onto the probably deserted beach and look down. If you're lucky, stretches of the black sand will be paved with glittering glass.

We hit what we considered a bonanza that day: not just your average white and brown and green, of which there were plenty, but amber and blue and aqua. There were shards of smoothed pottery and a few pieces of well-worn trash (the sea glass comes from a nearby dump), including an earpiece from some eyeglasses and what looked like engine parts. But mostly there was lots and lots of glass -- on the beach and stuck between the rocks.

The beach wasn't suitable for anything other than combing; the rocks would make swimming suicidal, and, when we were able to tear our gaze from the sand, the view wasn't impressive: Several gas tanks overlook one side of the beach.

But we spent little of our time looking up, the four of us scouring the beach like a quartet of crones, our backs curved and necks bent, we parents sporting sticks to help navigate the slippery rocks. The whole time we were there, we saw only two other people. We didn't talk, except to shout out discoveries: "Here's a big one!" "Here's a blue one!" "Aqua!" We found so much that, after we took photographs of parts of our collection, we left some pieces for future beachcombers. We didn't want to be greedy.

Stella Burgess, who is the Hawaiian cultural specialist at the Grand Hyatt Kauai Resort and Spa and one of the go-to people for information about Kauai, remembers when "everyone on the western end on Kauai would dump rubbish" on the outcropping next to Glass Beach. They would burn the trash and toss it into the ocean. The ocean then tumbled and threw back the trash, some of it rounded and sparkling.

"Nobody really paid attention to the glass," she says. "It just kept building on top of each other . . . . The whole beach was glass."

When she was younger, the glass was at least six inches deep. Folks used to go down there with five-gallon buckets and scoop it up to use in retaining walls and driveways. (Now there is a law that prohibits taking more than one gallon of beach sand per day for personal use.) As beach glass has become popular for jewelry and other crafts, artisans have found the beach and have raked it over.

On a visit this past summer, Burgess says, "it wasn't like I remembered it."

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While "sea glass" can be made in tumblers and acid baths, enthusiasts prefer the real thing. And Hawaiian sea glass is prized because of its unusual colors and shapes.

"Hawaiian beach glass in unique in that you can find more blues, and that's considered one of the more precious colors, if you can consider beach glass precious," says Sharon Umbaugh, a Sea Glass Association board member. She moved to the Big Island seven years ago from Ohio and sells sea glass on eBay and through her Web site, http://www.tropicalglass.com.

In addition, Hawaiian sea glass is usually "smooth and rounded, a bit like jelly beans, as opposed to the East Coast, where it's flat and ragged," Umbaugh says. "That's one of the reasons why it's so attractive and makes such beautiful jewelry, as opposed to the ones that are more shardy looking."

Umbaugh visited Glass Beach about six years ago. "It's a phenomenon, that beach, because it is really all beach glass," she says. "You can actually just scoop up handfuls of glass, and I've not seen it anywhere else." While Glass Beach may be unusual, she says, there are good sea glass sites all over the islands, although "any serious collector won't reveal their sources."

"There's a certain art to knowing where to look," Umbaugh says, but "on a good day for me, the ocean will just throw it at my feet."

Collector Hilda Morales also has a knack for finding sea glass. "You always have to be following the tides and the wind," she says. "If you see a lot of driftwood, a lot of coral, stop."

Morales, who lives on the northern side of Kauai, visits Glass Beach occasionally and remembers when you could scoop up the glass by the bucketful. Now it's more variable, she says. "Either you're lucky and you find bigger pieces, or you find tons of little pieces," she says. "I take everything."

Her collection, she says, is taking over her house. But sea glass has attracted her since she was a little girl in Acapulco, Mexico, where her mother called the bits of glass "mermaid tears."

I understand the draw. My older daughter, Rachel, and I made one more quick trip to Glass Beach later in the week. My younger daughter was sick, and I was thrilled to find a piece for her the size of a quarter and her current favorite color, aqua. When we got back to Maryland, the aqua piece went on display in Sara's room, and I filled a six-inch-tall triangular glass vase with my other finds in layers: the whites, then the pottery, then the blues and greens.

I knew I hadn't found anything too unusual; according to LaMotte's book, the rarest colors are orange, red, turquoise, yellow, black, teal and gray.

But LaMotte was kind enough to look at photographs of my collection that I e-mailed to him and had some encouraging words. The white pieces with tints of lavender, gray or pink could be pre-1930s glass, he wrote; I'd picked up some "neat pieces" of ceramic; and I'd collected some "tough to find" deep aqua colors.

That made me wish Kauai weren't 5,000 miles away, because by the time I get to Glass Beach again, there may be nothing left but sea and shore. What's happening at Glass Beach, it turns out, perfectly illustrates what's happening with sea glass itself, as customs change and both trash and treasure disappear in the relentless crush of time.

Elizabeth Chang last wrote for the Travel section about swimming with dolphins.