IAM ON ALL FOURS on the Lake Superior shore, ogling the contents of a pothole: pebbles and cobbles, water, and the sun’s direct rays. Shirt sleeves rolled, I survey the colors — muted purples, greens, yellows, and blacks. I choose a stone, then reach in to retrieve it. So the process goes: like a god selecting souls, I compile a handful of stones, then move to the next pothole to see what it has to offer.

When we get home, my husband buys two field guides: Is This an Agate? and Lake Superior Rocks & Minerals. I’ve never been adept at identifying rocks. This granite we found — pink and speckled as a kestrel egg — is composed of quartz, mica, and feldspar. There is feldspar again in a pepper-colored rock I think might be diabase, but here the feldspar is mixed with augite and possibly hornblende, magnetite or olivine. You can see how things get complicated.

The difficulty goes deeper than simple composition. When identifying a rock, you often must detect the almost unfathomable process that melded its minerals together. Several of my rocks could be quartz or metamorphosed sandstone — quartz subjected to high temperatures and pressure, which would make them quartzite. The only difference, my field guide says, is that quartzite has a little more texture. Identifying rocks, it seems, is more about parts than wholes, more about process than product. It is less about naming what you’ve found than about understanding how that thing came to be. In this case, how volcanoes, glaciers, and plate tectonics, over billions of years, produced and changed the rocks I hold in my hand. And how ten thousand years of wave action in Lake Superior smoothed them into something I want to take with me.

With flowers, categorizing is a simple matching game: look at the flower, look at the field guide picture. Is it the same size, shape, and color? Even birds, which can disappear in an instant, aren’t as perplexing to me as the rocks I can carry home to study with the aid of a library of reference books. Once, at a relative’s cabin in northern Wisconsin, an odd bird landed on the deck seemingly just to confound us. Warbler-sized, the bird was a bright olive green with black wings and tail, blotches of white on its underside, and speckles and blotches of neon orange on its throat, head, and belly. It looked like a parakeet. But even without internet, and with only a few generic field guides dug out of a neighbor’s basement, we identified it within three hours: a molting male scarlet tanager.

My understanding of rocks seems to go only as far as the broad divisions taught in grade school, and even on these categories I don’t have a firm hold. So I look up definitions. Igneous rocks are basically cooled lava. Sedimentary rocks are compacted, cemented-together pieces of other broken-up rocks. And metamorphic rocks are rocks that have changed form. A University of Oregon website states: “Just as any person can be put into one of two main categories of human being, all rocks can be put into one of three fundamentally different types of rocks.” Though the website clearly defines the rock types, it doesn’t say anything about the two categories of human being, and I can’t help thinking about the options that lie beyond the obvious divisions of male and female. Gay or straight? Accepted or marginalized? Convinced or uncertain?

I LIKE TO ROAM the forest naming things. Wood anemone. Rue anemone. False rue anemone. I wonder what makes the third one false: its more deeply lobed leaves, its slightly smaller flowers? It’s a buttercup, like the other two; but not, my Newcomb’s Wildflower Guide indicates, an anemone.

When I was an environmental educator, I taught a class called Stone Wall Study. I hiked my mostly elementary-aged students to a wall — one with its upper boulders spilled in the sun and gaps through which two could pass abreast — and asked them to speculate on the wall’s original purpose, as well as to investigate the distinct habitats it now delineated. On one side was a red pine plantation; on the other, a mixed deciduous forest. Which side of the wall looks more natural? I would ask. Did the wall keep something out or something in? Once, during the class, I thought I had discovered a new species: on the wild side of the wall was what looked like an anemone with multiple tiers of petals, its flower a fancy petticoat, like some kind of double hybrid. When I couldn’t find it in my books, I brought a local biology professor to check it out. Not a new species, he said, just an anemone with some kind of odd gene.

I don’t know how well my students could imagine the farmer’s sons who dutifully dug the rocks from the soil and piled them on the wall to provide safety for a few dairy cows, or the Civilian Conservation Corps crew that planted the red pines in the deserted pasture one hundred years later. Even with more life experience than my students, I myself have trouble imagining what I can’t see, and what has occurred over a period of time longer than a lifespan. I am baffled by the process that created the rock, known as Shawangunk conglomerate, of which this particular wall was composed. I’ve always been plagued with a mental deficit for understanding composition, processes, and change — the kind of thinking the stones I have brought home from Lake Superior also demand — and this deficit has extended far beyond my ability to properly identify our planet’s rocky foundations.

All my life I’ve battled a sort of dyslexia of cause and effect. On a recent canoe trip, I was mystified by a high browse line on the trees overhanging a lake. Did the deer stand in the water and dine? How tall could the deer possibly be? I wondered, until someone explained that in winter the lake froze, and they walked across the ice to graze. A weirder example: growing up in the early ’80s, I lived for a while under the fear that contracting AIDS turned you gay. My older sister set me straight, telling me AIDS actually killed you. It didn’t make you gay; gay people got it. I was, initially, relieved: if I contracted AIDS I wouldn’t turn gay, only die. (Now, older and away from religious and family creeds, this response, of course, is embarrassing.) But almost immediately a seemingly darker worry surfaced: without a disease to cause homosexuality, how could I be sure to avoid this “affliction”? (For, at the time, that is what I had gathered from society that homosexuality was.) “How do you know if you’re gay?” I asked my sister. The question arose from a presexual mind — one that couldn’t yet fathom romantic love or physical attraction to anything. “You just wake up one morning and you know,” was her response.

I couldn’t understand how one day you would not know and the next you would, so I imagined it must be like getting your period — a milestone still many years off for me. I assumed you would open your eyes one morning and pull back the covers to reveal, on the bed sheets, written in blood, the universe’s edict: gay or straight. I believed you had no say in the matter, that the issue was as tightly and long-ago cemented as a conglomerate’s quartz and pebbles.

The issue, though, is much more complex. Some evidence does point to sexual orientation as something people awaken to — an inborn predisposition. Identical twins are more likely to both be homosexual than fraternal twins or non-twin siblings. And having several older biological brothers — whether you live with them or not — slightly increases a man’s chance of being homosexual (from 3 percent to 5 percent), implying that the cause occurs prenatally. However, sexual orientation and sexual behavior are also considerably influenced by social and cultural factors. Among the Marind-anim people of southern Papua New Guinea, teen boys freely engage in homosexual relations with each other and with older married men, whereas all women are presumed heterosexual. In ancient Greece, men in their twenties permissibly wooed boys whose beards had yet to grow.

Perhaps my childhood fears were influenced by a society focused too much on sex and not enough on love. As it turns out, recent research and theory indicate that human sexuality — especially women’s — may harbor a subtle plasticity. Whether you fall into the category of heterosexual or homosexual, your sexuality may include a secondary characteristic that enables you to fall in love with people who contradict your sexual orientation. Regardless of any “odd” genes or environmental conditions (in womb or world) that may lead to one or another sexual orientation, love, it appears, is ultimately metamorphic.

ON THE NIGHT OF March 30, 1778, in Woodstock, Ireland, twenty-three-year-old Sarah Ponsonby donned men’s clothing, grabbed a pistol and her little dog, Frisk, then climbed out the parlor window of the Georgian mansion where she lived with the family of her first cousin, Irish aristocrat William Fownes.

Twelve miles away, at Kilkenny Castle at ten p.m. that same night, thirty-nine-year-old Eleanor Butler, daughter of one of the period’s most powerful Irish families, also put on men’s clothing and secretly mounted a horse bound for Woodstock. Once there, she hid in a barn and waited for her dear friend. Avoiding unwanted marriages, they planned to travel twenty-three miles to Waterford, board a boat for England, and withdraw to the countryside to live together. Their escape did not succeed. The two women were returned to their families, who were relieved that the elopements did not involve men, which would have undermined the ladies’ honor.

Sarah and Eleanor persisted, though, and openly now, in their desire to live together. Threatened with being sent to a convent, Eleanor escaped again, fled to the Ponsonby estate, snuck in through a hall window (aided by a housemaid), and hid in Sarah’s closet. A day later she was discovered, but instead of coming to retrieve his daughter, Eleanor Butler’s father sent word the two women could go away together. For ten days the Fownes family resisted, but when Sarah declared at all costs her one desire was “to live and die with Miss Butler,” they too relented. Early on a May morning the two ladies left, with Sarah’s housemaid, in a coach provided by the Butlers. Their journey ended in Llangollen, Wales, where they lived together for fifty years, studying literature and languages, writing letters and diaries, helping the poor, gardening, and running a small dairy. Despite keeping to themselves, they became widely known as “the ladies,” and later “the Ladies of Llangollen.”

For over a century, people have tried to identify what these two women were. Were they lesbians or, as we so diminutively tend to put it, were they just friends?

ATTEMPTING TO IDENTIFY my rocks, I pause at a page in the field guide between Jasper and Laumontite titled Junk. It is structured the same as every other page, with a map depicting junk’s occurrence along Lake Superior in the upper right corner and the same headings, like HARDNESS and STREAK, in the left margin. Next to SIZE the text reads: “Beach junk can be as small as a shard of glass or as large as furniture or appliances.” Next to WHERE TO LOOK the book says, “You can find beach junk all around the shores of Lake Superior.” It’s amusing to me that beach junk, though its name implies a lack of value, is important enough to have garnered a page in the guide and that, although the idea of beach junk having a universal hardness or streak is ludicrous, an attempt has been made to mold such a find into the accepted classification system of rocks and minerals. But I’m confused by the accompanying picture, which shows a porcelain tile, beach glass, rusty metal, an aluminum blob, slag glass, and a piece of driftwood. How does driftwood — something natural, something people collect — fit into the same category as discarded furniture and appliances — basically trash? I suppose it’s all about perspective. Like being “just friends” when you might be lovers, to a rockhound, even driftwood is junk.

MOST SCHOLARS call the eighteenth-century relationship enjoyed by the Ladies of Llangollen “romantic friendship” — a particularly intense, exclusive, intimate, asexual love between same-sex friends (either male or female) that may or may not include holding hands, cuddling, kissing, cohabitating, and sharing a bed. Though the term “romantic friendship” did not come into use until the nineteenth century, passionate nonerotic friendships had already existed and been considered ordinary for some time: Plato describes them in his Symposium, circa 385 bc; Montaigne describes them in his essay “Of Friendship,” dated mid-sixteenth century. During Victorian times, romantic friendships flourished between middle- and upper-class women, likely because Victorian men and women — even married couples — resided in two opposing worlds, marriages were often arranged, divorce was rarely sanctioned, and women were assumed to be uninterested in sex. Thus, ardent female friendships — like the relationship between Eleanor Butler and Sarah Ponsonby — were tolerated and even encouraged.

These relationships have been tagged with all sorts of labels. Intimate friendships between college-aged women were termed “smashes” in nineteenth-century literature. “Boston marriage,” another widely used phrase, originated in Henry James’s novel The Bostonians. The phrase “mummy-baby friendships” comes from studies in Lesotho, South Africa, where intimate relationships between younger girls and slightly older girls are part of the female social order. Yet another name, “Tom-Dee relationships,” is borrowed from Thailand; Tom is short for tomboy, and Dee for lady.

Even though contemporary America does have terms for intimate, nonsexual, same-sex relationships, such as “bromance” and “womance,” it’s hard for the modern American mind to understand and accept the concept. In the school where I teach, students titter at the way Brutus and Cassius speak of each other in Julius Caesar, throwing the words love and lover around shamelessly. According to Lillian Faderman, author of Surpassing the Love of Men: Romantic Friendship and Love Between Women from the Renaissance to the Present, society began scorning intimate same-sex friendships around 1920: “Such friendships are usually dismissed by attributing them to the facile sentimentality of other centuries, or by explaining them in neat terms such as ‘lesbian,’ meaning sexual proclivity. We have learned to deny such a depth of feeling toward anyone but a prospective or an actual mate.”

As Faderman implies, everything today must be about sex. The idea of romantic friendship washes up on the shores of our post-Freudian era like so much beach junk, its field marks smoothed through the last century into something difficult to identify but simple to lump into a single, discriminatory category: latent homosexuality.

THE LORD’s PRAYER of metamorphism goes like this: limestone to marble, sandstone to quartzite, shale to slate, granite to gneiss. I can recite it as if I am practicing for some kind of religious confirmation. But even as I utter the words, I don’t really understand them. I remember the rock cycle. Igneous rock can become sedimentary or metamorphic. Sedimentary rock can become igneous or metamorphic. Metamorphic rock can become igneous, sedimentary, or even a new kind of metamorphic. But I am baffled by any description of how these processes actually work.

Limestone to marble, sandstone to quartzite, shale to slate, granite to gneiss. I recite the words again. At what point does the granite become gneiss? On what day? At what hour? That old dyslexia kicks in. Where is the line or the moment in time that divides what it once was and what it now is? Metamorphism, my source says, is impossible to observe; it can only be studied after some sort of weathering, erosion, or uplift. Often the processes that caused the change are tricky to discern. And metamorphism is not sudden; it takes millions of years for rocks to change.

The changes that we suffer within ourselves can be just as incomprehensible. For a heterosexual, falling into a particularly intimate friendship with someone of the same sex (or, for a homosexual, someone of the opposite sex) can lead to a small crisis of identity when considered within the restrictive categories we currently use to describe relationships and sexuality. When Basil Hallward first saw Dorian in Oscar Wilde’s The Picture of Dorian Gray, he stated, “I knew that I had come face to face with some one whose mere personality was so fascinating that, if I allowed it to do so, it would absorb my whole nature, my whole soul, my very art itself.” I have met a woman like this.

SHE IS WHERE I have never been. She is almost always where I have never been. This time it is Biakpa, Ghana. Her husband is ill, in bed. She reads and looks for insects. She feeds grains of rice to three types of ant colonies, watches snails mate, finds a cigar-sized millipede. There are moths whose wings look like animal eyes or dead leaves, a green bug that looks like a green leaf, huge spiders, a caterpillar that hangs upside down from the ceiling with a tube that covers its body. Hard-skinned grubs stick to both the ceiling and the cement wall; their colors match what attracts them. She and the local kitty hunt in the evening. Where she crouches and looks, it crouches and looks, then it kills what she sees.

I know this because she has written me. In fact, what I have written above is almost entirely plagiarized — her version of herself, which she meant for only me to see. What I remember is her turning to laugh as she locked the cabin door before a hike during a three-day weekend in the woods, no husbands, in Michigan’s Upper Peninsula. I was startled because I saw age in her face. The last time I had felt so close to a friend I was young. And this woman was as old as my mother was then, and I am old enough to be my mother then, and neither of us are mothers — which is beside the point, but maybe it isn’t. Inside us are half of each child we’ve never had and some small piece of all the women we’ve descended from. When I admire the distal edges of her fingernails, white and perfectly curved like the horizon of Ely, Minnesota, must have been the weekend she went mushing — which I read about on her travel blog (also there: a picture of her juggling with dried mud for some children along the Mekong River) — when I admire these things, it is because I love her passion for living.

One night, we are actually in the same place: full of seafood and wine, seated between our husbands at the musical Wicked. When the lovely Glinda, who becomes the Good Witch, sings to the emerald green Elphaba, future Wicked Witch of the West, “Because I knew you, I’ve been changed for good,” she whispers, “That’s us!” and grabs my hand. I am taken by surprise. I whisper back, joking, “I guess I’m Elphaba.” I say this because my friend is beautiful: hair the almost-black of the basalt I brought home from the lake, eyes as blue as the kind of cloudless sky that almost everywhere, you must patiently await.

For one week, in the month of July, I go to where she is. To her favorite place on earth: high desert, a place that’s made of circumstantial evidence — dry riverbeds, already eroded buttes and mesas, a beauty mute and built on abstinence. She plans a ten-mile loop hike at Capitol Reef National Park, which sounds marine but water is scarce here. We don’t have four-wheel drive so we have to hike five extra miles, round trip, to and from the trailhead. My husband comes along. Her husband stays back — at the end of our hike, he will meet us on the road, the blue plastic tub they use to wash their camp dishes filled with ice and a two-liter Diet Coke.

None of the dreams I had of hiking side-by-side, steeped in conversation, pan out because I hike much faster than she, especially on the uphills, which once or twice have made her faint. We hike to the lip of the waterpocket fold, a hundred-mile-long gash in the earth’s crust, the rocks on one side lifted seven thousand feet higher than the other. It is dry, beautiful, alien. But by the end of the fifteen miles, I trail behind her and my husband, in so much pain I am crying. It’s because of the pounding, she says. These are not the soft soil trails of the forest. Everything is rock.

She is where I would like to be. I do not mean that she is there. I mean that she is this thing: a sun-warmed rock next to a rushing stream — a rejuvenating combination of sunlight, stone, and water. When I travel, I seek out these things. Likewise, she is where my mind goes when it decides to wander.

CONSTANT THOUGHT about the object of desire is a common sign of romantic love, as are a need for proximity and physical contact, despair at separation, elation when the object of desire gives you attention, and a tremendous awareness and understanding of the partner’s moods. But in the article “What Does Sexual Orientation Orient?” Lisa Diamond points out that these feelings and behaviors also characterize the infant-caregiver bond. And who has not heard a new mother comment that she is totally “in love” with her child? Although we may not remember it, we were in love with our parents, too, during the first year or so of our lives.

The mistake most of us make is to assume romantic love evolved to ensure that mammalian mothers and fathers stuck together to raise their highly dependent young and, thus, that it occurs in concert with sexual desire, and is only legitimate when directed toward the opposite sex. But it’s likely that romantic love between adults is what’s known as an exaptation, a trait evolved for one reason but co-opted for something else. Here’s why: from an evolutionary standpoint, long before there was “mating for life” there was the necessity for a mother to bond with her child — creating a totally physical, totally loving, but totally asexual relationship between her and either a daughter or son. The point here, as Lisa Diamond puts it, is that “romantic love and sexual desire are functionally independent,” and “love knows no gender.” In fact, humans may be biologically predisposed to experience romantic friendship.

THE UNIVERSITY OF OREGON website that divided humanity into two undeniable (but unstated) groups gave this definition for metamorphism: rocks that have “moved into an environment in which the minerals which make up the rock become unstable and out of equilibrium with the new environmental conditions.” So metamorphism is situation-dependent. It’s the process of adjusting to some kind of change, usually caused by increased temperature or pressure. Above 200 degrees Celsius (392 degrees Fahrenheit) rocks begin to recrystallize. Whatever elements are available in the original rock will be broken down and recombined in a different way, creating new minerals.

If temperatures reach 600 degrees Celsius, a complete meltdown occurs: rocks become magma, which, when it cools, creates igneous rocks, something entirely new. But during metamorphism, nothing is lost or added at the elemental level. The basic composition stays the same, which is what is so complex about it: that the rock can still be what it is and yet be in the process of becoming something slightly different. What I don’t get about metamorphism, that the metamorphism takes place while the rocks are in a solid state, is also perhaps what is so groundbreaking about new theories on human sexuality: according to Lisa Diamond, it is possible for a person’s sexual desire to change in the context of a single relationship while that person’s sexual orientation remains the same.

Diamond has coined the phrase “sexual fluidity” to describe this phenomenon. In her book by that name, Diamond addresses how most people believe that the biological order of a romantic relationship entails sexual desire first (that initial “chemistry”) and romantic love (the intimate bond) second. But, Diamond’s research shows, the opposite can also be true, especially for women. What begins as an intimate friendship can turn sexual. Different from bisexuality, which involves regular attraction to both sexes, sexual fluidity might happen only once in a lifetime, or only a few times, or not at all. The likely catalyst is oxytocin, a hormone that facilitates not only bonding between infants and caregivers (or close friends), but also sexual arousability. Simply hanging out with someone for whom you care deeply can — sometimes and for some women — produce desires that conflict with a person’s primary sexual orientation. In other words, the body’s chemistry can temporarily change its own seemingly fixed tendencies. When this happens, the world may call you something different. But you are still you.

IF YOU SEARCH Elizabeth Mavor’s biography of the Ladies of Llangollen, or the diaries of the ladies themselves, you won’t find a single hint of anything sexual. And neither will you here. All I can say is this: there is no field guide for love, or friendship, or the great variety of people one will encounter in a lifetime. And: this is not a coming out piece. It is about going inward.

One Christmas, we go with our husbands to Les Eyzies-de-Tayac, France. I want to see the engravings of early man, something inconceivably old. I arrange a visit to the Grotte de Bara-Bahau — an onomatopoeic name, given for the sound the large rocks that have fallen inside the cave must have made. We listen to a woman give a brief tour to just the four of us, in broken English. We strain to see in the rock the living things she traces with her laser pointer: a reindeer, a horse without legs and a horse without a head, and aurochs — an early ancestor of cattle. The bear is a bit easier: natural convexities in the cave wall itself form its head and shoulders, a large flint pebble acts as eye, and from its mouth is etched a long line, representing the animal’s breath. Easier still is the phallus, which my friend points out privately to her husband before the guide even gets to it, not sure if it is an actual engraving or an instance of pareidolia — the imagined perception of a pattern or meaning where it does not actually exist, like seeing a picture in the clouds. “Oh, yes,” the guide chimes in, overhearing. “There is a phallus.” This is rather rare; more common are depictions of female genitalia, I later read.

We leave the cave, joking like teenagers about my friend’s singlehanded ability to identify the phallus in a cave of otherwise obscure engravings, but also about the strange question our guide repeated over and over during the tour, singling out each one of us, multiple times, as its recipient. “Do you know?” she would ask, the intonation and pronunciation of her mother tongue adding mystique to her inquiry. Then she would turn to the next one of us, making direct eye contact: “Do you know?”

“I do not know,” she would respond to her own question. She seemed to want to preserve, in addition to the engravings, some other element of the cave’s mystery.

ON THE SHORE of Lake Superior, among those wave-carved potholes filled with stones, I looked in, chose the ones I liked, and held them close. But just as the page on beach junk in my field guide suggested, I also found something in one of those potholes that I didn’t expect. When my husband accidentally dropped a coveted quartz pebble into the largest and deepest of the holes, I rolled up my shirt sleeve as far as it would go and leaned over to recover the stone. Suddenly, I saw myself.

It must have been similar to what Narcissus experienced in that silvery-surfaced forest pond. Never before had I seen a clearer picture than what I saw that day in the pothole. I couldn’t move. Like Narcissus, all I could do was gaze. Perhaps what kept Narcissus at the pool, in admiration over what was before him, was not self-love but a fascination with the image of himself as reflected by the earth. What I saw in that pothole, now a portal, was not made of skin and bone — the usual “junk” — brown hair, brown eyes, small ears, my father’s nose. I was made of water and stone. Though we may label ourselves heterosexual, bisexual, homosexual, lovers, or just friends, we should not be surprised to find that we are as dynamic as the earth that holds us up. We are simultaneously solid and fluid, inherently uncategorizable. We are always in the process of transformation.

Originally, life on earth was divided into two kingdoms: plants and animals. Then there were three; then four; then five; now six. Perhaps two categories — whatever they may be — are not sufficient for humans either. Names that come from without are destined to be inaccurate. It is not what we are called that we must answer to, but what calls us from within.