Volcanic Rocks Add Sizzle to Seafood Soup in Mexico

Adding red-hot volcanic stones to a broth of seafood and other ingredients creates a feast for the eyes and the taste buds of customers at Las Jícaras del Huanacaxtle restaurant in San Cristóbal de las Casas, a major city in Mexico’s southernmost state of Chiapas. Willi Flores Martínez, the restaurant’s owner and manager, advises the utmost care in choosing the stones and the wood for heating them.

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Volcanic Rocks Add Sizzle to Seafood Soup in Mexico

Adriana Alcázar González, GPJ Mexico

Caldo de piedra, or stone soup, is a specialty at Las Jícaras del Huanacaxtle restaurant in San Cristóbal de las Casas, Mexico. The soup is served inside the gourd of the jícara fruit and is heated by red-hot, volcanic river stones that are dropped into the dish just before it is served.

SAN CRISTÓBAL DE LAS CASAS, MEXICO — A waiter walks steadily among the tables of Las Jícaras del Huanacaxtle restaurant while carrying a jícara gourd filled with boiling-hot soup. Steam from the soup wafts amid the tables. The aroma, a mixture of cooked fish, crab, shrimp, mumo leaves (which have a licorice flavor) and red-hot volcanic stones, washes over the customers.

“We even cook the stones,” says William Flores Martínez, laughing. Flores Martínez, also known as Willi, is the owner and manager of Las Jícaras del Huanacaxtle, which serves “caldo de piedra,” or stone soup, in San Cristóbal de las Casas, a major city in Mexico’s southernmost state of Chiapas.

Stone soup often includes broth, fresh seafood and hot stones, which he says impart a special flavor into the dish while heating the other ingredients.

Flores Martínez says the dish originated in San Felipe Usila, a municipality in the neighboring state of Oaxaca, which is more than 625 kilometers (388 miles) from the restaurant. He lived in Oaxaca for more than 14 years.

When he visited San Felipe Usila, he saw fishermen cooking a soup of fish and shrimp with red-hot stones in the kettle, he says. After he tried the soup, his amazement only grew, he added. Years later, he brought the flavors and techniques for making stone soup to this stone-cobbled community.

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Adriana Alcázar González, GPJ Mexico

William Flores Martínez, or Willi, is the owner of Las Jícaras del Huanacaxtle. He believes hot volcanic stones, seen here, are essential for the soup, not just because of their heat, but because they impart a special flavor to the dish.

Flores Martínez says stone soup revealed to him the secret that the flavor of a dish depends on the quality of the ingredients, the cooking method and the cook’s seasoning and ingenuity.

“In order to make a good stone soup, you need to include the best fish, the best shrimp and the best crab. But you also have to take into account the type of rock you will use and the type of wood with which you will heat up the stones, because the stones will be saturated with the wood’s ashes,” he says.

Flores Martínez recommends stones from a river with volcanic origins, because it ensures that the limestone will break up when it comes in contact with the fire. The stones should be heated over oak, he added.

“I only use oak wood to heat the stones. I would never use pine, because its oil gives the food a slightly bitter taste,” he says.

Flores Martínez has a stock of nearly 500 volcanic stones, each of which he uses about 10 times, he says. After repeated use, they crack and break easily in the broth and have to be discarded, he says.

The vessel in which the soup is cooked is also important, says Flores Martínez. He prefers to use dried gourds from the jícara tree, commonly referred to in English as the calabash tree. The jícara fruit is roughly the size of an adult hand, though some can be larger.

For Flores Martínez, a good cook is someone who manages to combine passion, taste, knowledge and delight for customers. He believes caldo de piedra, the stone soup is a dish that manages to awaken sensations and flavors just by its appearance.

“For the customers, it’s amazing to observe the cooking process and the boiling that the red-hot stones provoke between the fish meat and the seafood,” he says. “Seeing the soup boil in front of them is not something they can commonly enjoy.”

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Adriana Alcázar González, GPJ Mexico

At Las Jícaras del Huanacaxtle restaurant, Fernando García Gómez, the assistant chef, prepares the stone soup, one ingredient at a time, as he cuts the mumo leaves to place into the gourd.



Cooking pot or large saucepan

1 knife

1 jícara gourd. If you don’t have a gourd, use a bowl that can withstand heat

4 medium-sized volcanic stones (about 1-2 inches in diameter), preheated for 2 hours, preferably on oak

Tongs for transporting the hot stones


180 grams (3/4 cups) of dried shrimp

¼ of a piece of mojarra, or tilapia, cut into pieces

¼ crab, focusing on using the meat from one section still in the shell

1 tomato, chopped

1 onion, chopped

1 sprig of epazote, a leafy herb

½ a leaf of mumo. Can use anise, or yerba santa as a substitute

1 medium clove of garlic, chopped

4-medium-sized volcanic stones

Salt to taste


½ liter (2 cups) of water

2 red tomatoes, chopped

1/8 of an onion, chopped

1 epazote twig

2 dried guajillo chilies, chopped

1 sprig of epazote, a leafy herb. Can use tarragon as a substitute

1 cup tomato sauce

Salt to taste

Makes 1-2 bowls


How to make William “Willi” Flores Martínez’s Caldo de Piedra

  1. Combine the tomato sauce with the guajillo chili
  2. Mix the water, tomato sauce and half of the onion in the blender for three minutes.
  3. Place the mixture in a pot or saucepan, and cook on medium heat for 10 minutes. Then let it stand at room temperature.
  4. Place the fish, crab, mumo, epazote leaves, chopped tomato, garlic and guajillo chilies into the gourd or bowl. Add broth from the pot, but leave enough room for the stones to be put in.
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    Adriana Alcázar González, GPJ Mexico

    The soup has been assembled, with epazote leaves added to the broth. It now awaits the hot stones.

  5. Lastly, add the hot stones. The stones should be put in one at a time, in intervals of approximately one minute between each stone.
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    Adriana Alcázar González, GPJ Mexico

    William Flores Martínez heats up a volcanic river stone over his restaurant fire. In order to achieve the perfect flavor, he says he uses oak in his fire.

  6. When all the stones have been put in, let the soup simmer for one more minute – about five minutes in total, with four stones – and then serve!
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    Adriana Alcázar González, GPJ Mexico

    Upon impact, the hot stones bring the soup to a sizzle. After the final stone has been added, the stone soup is brought to the customer’s table. It’s a rare and pleasurable experience for many of Las Jícaras del Huanacaxtle’s customers.

A final word from Flores Martínez:
“What I like about this dish is the cooking process. With the hot stones, it looks like a hot spring to the client’s eyes, and the expression on their faces is unforgettable.”


Rishi Khalsa, GPJ, translated this article from Spanish.