Crystals have been at the forefront of recent fashion and wellness trends. Celebrities are putting traces of these mineral rocks into their new perfume products while numerous physical and online stores display entire chunks of crystals, advertising their supposed healing powers and energy.

But people’s fascination with crystals and other gemstones dates back thousands of years, and Stanford scholar Marisa Galvez is digging into how and why that obsession started.

Galvez, an associate professor of French and Italian, is working on a comprehensive history of the relationship between people and crystals through the centuries.

“The physical qualities of crystal make it stand out among other stones,” Galvez said. “Its ability to refract light and its transparent but dark appearance are partially the reason why so many different cultures and societies prescribed magical powers to this stone.”

Galvez found that some poets and authors during the Middle Ages used imagery of crystals in their writing in an unexpected manner. Aside from being commonly viewed as an embodiment of purity and perfection, crystals were also used by some medieval poets as a way to examine desire and the uncertainty of love, Galvez said.

Stanford News Service interviewed Galvez about her research.

What inspired you to start this research?

It happened sort of randomly. I was talking to a friend who is now an architect in New York. She asked me if I knew anything about the history of crystals because she noticed that many 20th-century architects and writers, such as Paul Scheerbart, Bruno Taut and Ludwig Mies van der Rohe, were fascinated with crystals. They were inspired by medieval stories about crystal and fantasized about transparent crystal skyscrapers and utopian cities made of glass.

I became curious. What other legends about crystals are out there?

We already know from other scholarship that crystal symbolized spiritual purity and perfection and was often used in religious contexts, especially in Christian churches where it was used to decorate Gospel books and other important religious items. But that wasn’t the only way people viewed crystals.

What is the biggest takeaway from what you’ve found so far?

The most ancient writings that mention crystal include the accounts of the Roman historian Pliny the Elder, who described different precious stones, their origins and physical qualities. The word “crystal” comes from the Greek krystallos , literally meaning “coldness drawn together,” or a kind of ice.

In Western Christianity, crystal was often mentioned in writings and used to decorate important religious objects, as it was thought that crystal manifested transcendence and the light of the heavens. For the religious, the stone symbolized purity, faith and perfection. For example, it was used to described the purity of the Virgin Mary.

In my current focus on the writing in the 12th and 13th centuries, I find something even more interesting. Medieval troubadours played around with the symbolism of crystal. They used the stone and its qualities to describe the beauty of the main character’s love interest in their stories. But they also used crystal to describe different aspects of carnal desire and love.

As an example, one piece of writing I found draws a parallel between the uncertainty one can feel when falling in love and the uncertainty one experiences when looking through a transparent but cloudy crystal, unsure what he or she is seeing.

What is your favorite use of crystal symbolism that you’ve found so far?

I was surprised to find out how 12th-century poet Bertran de Born compared the teeth of a woman he described in a passage to crystal. In this lyric, titled “From now on, you shouldn’t spend a whole morning eating,” the troubadour uses crystal to signify the sensual pleasures of courtship.

From the passage: “By the charming conversation and the beautiful smile she gave me, when I saw her teeth of crystal and her body, slim, delicate, and fresh and smooth, so pretty in her tunic – and her color was fresh and rosy – she locked up my heart.”

Reading that passage makes me think of a woman with a set of bright grills. It’s quite surprising. We expect him to say her face is like crystal, but there is something carnal about crystal teeth. The image helps us understand that poets were attune to the physical qualities of crystal and translated that into erotic desire.

Why is it important to do this research?

Understanding the history of how crystal was perceived by different people throughout human history informs why we are fascinated with this stone to this day.

Aside from its more obvious symbolism of faith and innocence, crystal was also a material for thinking about – and not merely representing – erotic love. Even in descriptions of exotic “Eastern” architecture in medieval texts, the crystalline qualities of fountains and buildings evoke mystery, uncertainty and desire. This was probably because the stone itself has contradictory aesthetic qualities. Crystal is transparent but you need to put effort in order to see through it. It refracts light, but it can also emit light.

I think medieval poets were inspired by these ambiguous qualities, so that’s why they used crystal as a symbol and a medium to examine desire and love.

Why do you think people are still obsessed with crystals to this day?

People have always had this fascination with precious stones. But people latched on to crystals partly because they have these contradictory physical qualities: They are both dark and transparent. You can see through them, but not really.

That history helps explain the continuing contemporary obsession with crystals and how they are thought to have magical, healing effects and energy.

In the Middle Ages, people also thought that crystals would bring a spiritual presence. People had this hunger to have something physical that embodies faith and spirituality.

People still have that hunger now, and that’s why crystals are so popular. Crystals, in a way, fulfill a spiritual need for some people. Some people go to church, some do yoga, and others collect and meditate with crystals.