Stories in Stone

by David B. Williams

  At long last recognizing that wood forts were unsafe and expensive to maintain, Spain approved a request for ten thousand ducats and twenty-four slaves to build fort number eight of coquina in 1595. Twenty slaves, one master stonecutter, one apprentice, and three masons were to arrive from Cuba.13 On September 22, 1599, a storm surge tore away part of this new fort, which for reasons unknown had been built not of coquina but of “wood, sand and flour sacks.”14 Uncharacteristically, the rebuilt fort—number eight—survived, perhaps because slaves and subjugated natives regularly repaired and rebuilt the walls.

  In addition to building with inadequate materials, Augustinians had to worry about a new potential threat when the English landed at Jamestown Island in May 1607. The new settlement’s success guaranteed that England would spread out along the East Coast and eventually contend with Spain for dominion on the continent.

  Fort number eight finally collapsed and St. Augustine fell on hard times during the mid-1600s. The garrison shrank to 150 soldiers, who had been reduced to foraging for roots. On May 28, 1668, a supply ship arrived just outside the harbor and, as was customary, signaled the harbor pilot to come out in his launch. The pilot found his countrymen onboard and signaled the good news to town with two gunshots. Everyone relaxed and celebrated that food would soon arrive.

  When the pilot boarded the supply ship, he discovered that pirates under the command of Robert Searles had overpowered the crew. Searles and his men overwhelmed the unprepared town and took what little they could find in St. Augustine, though they didn’t raze the town or the fort. Instead, they vowed to return with more men and ships and use St. Augustine as a base to capture trade boats sailing the Florida Current.15

  Searles’s action and proposed return scared the bejesus out of then Florida governor Guerra, who wrote out a request to Spain for money and permission to build a stone fort. Guerra had one problem: Searles had taken all the sails necessary to equip a warship to sail to Cuba, the closest major Spanish port, so Guerra had to rely on the harbor launch to head out into the Florida Current and hope to meet a Spanish ship bound for Cuba. Captain Menéndez took the launch on July 8. It sank the next day and he walked back to town. A month later, after borrowing every scrap of sail that could be found,Menéndez sailed out in the lone warship. He reached Havana on September 9.

  Havana provided some money and food, but Menéndez had to travel to Mexico and the capital of New Spain to get more money and permission to build a new fort. He arrived in Mexico City in early November 1669. Working with all diligent speed to defend Spain’s most critical Florida settlement, the viceroy approved sending twelve thousand pesos and men from Cuba on December 16, 1670. In the intervening year the Spanish government had appointed a new Florida governor, sent three royal decrees saying that a fort should be built, heard rumors that St. Augustine had been destroyed (which delayed a shipment of soldiers and food), and debated whether the queen had expressly said to send money for the fort or merely thought it was a good idea. The queen’s attorney in Mexico raised this last point.16

  Outside events again affected St. Augustine. In April 1670 English ships landed at the Ashley River and established a small town, named in honor of their king, Charles II. Charles Town was only two days’ sail from St. Augustine and within Florida’s territorial border. In addition to pirates, the Spanish had to fear colonists.

  Six months after the viceroy’s approval, Florida’s new governor, Manuel de Cendoya, sailed from Mexico and arrived in Havana on June 29, 1671. Havana would provide masons, stonecutters, and lime burners, plus military engineer Ignacio Daza, who would be in charge of building and designing the new fort. Cendoya finally reached St. Augustine on July 6, 1671, over three years after Searles had pillaged the town. Luckily the pirate didn’t keep his word. Cendoya arrived with money and fifteen stoneworkers, but no Daza, who was not scheduled to come north until August 1672.

  On July 12 Cendoya ordered work to begin on the fort.17 He wanted 150 Indian laborers (peons) to assist the fifteen Cubans. Fifty men would quarry and transport coquina; fifty would make lime; and fifty would cut stone and dig the foundation trench. Blacksmiths made axes, pry bars, shovels, picks, and wedges. Carpenters built baskets, boxes, buckets, and square-ended dugout canoes. To make lime, the Spanish collected oyster shells and burned them in kilns, which drove off carbon dioxide and left behind a white powder.

  At the quarry on Anastasia Island, the first task was to clear away the scrub oak, palmetto, and rattlesnakes and reach the coquina, which lay under a thin layer of soil. Peons used axes and picks to cut grooves deep into the soft stone. They pried out blocks with wedges and pry bars, taking advantage of layers of sand within the coquina that formed a natural splitting surface. A waterlogged block, two feet thick by four feet long, required six men to lift it. Workers transported the blocks by cart to a creek, where they loaded the stone on boards laid across the canoes. On the far shore north of the fort, more men unloaded the blocks, which needed to season for at least a year.

  Workers also proceeded with lime production essential to making mortar. By March 1672 the kilns had generated sixty-three hundred bushels of burned-down oyster shells. They had most likely been collected from shell middens that dotted the coast. Native people, who had inhabited coastal Florida for thousands of years, relied heavily on oysters in their diet and had generated the shell mounds, which could stretch for several hundred yards in all directions and rise tens of feet.

  Engineer Daza finally arrived from Cuba in midsummer. Governor Cendoya, Daza, and other dignitaries broke ground for the foundation trench at four P.M. on October 2, and on November 9 they laid the first block of coquina. Everything was ready for quick construction of the castillo made of clamshells.

  Coquina around St. Augustine is like George Washington on the East Coast: everyone wants to claim a connection. You can live in a planned community at Coquina Crossing, bowl at Coquina Lanes, and pray at Coquina Community Church (based on a “more reliable foundation stone, that of Jesus Christ”). You can buy bags of coquina, too. The city visitor center offers a better deal than the national park. For $2.83 you get two marble-sized bits and a confusing fact sheet that calls coquina both a “natural limestone” and a “rocklike substance.”

  You can also visit three sites on Anastasia Island with signs stating that stone for the castillo came from that particular location. A coquina chimney and an old coquina well filled with trash stands near one sign. Nothing nearby looks like a quarry. Another sign stands near a swimming-pool-sized pond, a good spot to see great blue heron stalking small fish.18 Again, no surface feature indicates that this might be a quarry. The third seems the most likely, with low slopes of coquina rising from a one-hundred-yard-long, fifteen-yard-wide shallow depression. It is also the best-marketed site, with prominent signs and two brochures describing its history.

  Considering the size of the castillo—Joe Brehm said that a geologist estimated that over five billion pounds of stone had been used to build it—each of the signs is probably correct. What may be more surprising is that more sites don’t make the same claim.

  Site number three is on the northwest edge of Anastasia State Park, on the east shore of the island. A carved wood placard nailed to a slatted fence designates the area as “Old Spanish Coquina Quarry.” Behind the sign runs a flat, shell-fragment-covered path, which curves through two hundred feet of scrub oak and palmetto into a clearing. If you arrive early in the morning, the sun may backlight mist rising from warmed grasses and low shrubs growing in the quarry bottom.

  About sixty feet from the opening, a slope of tan to white shells and shell fragments weathers out of a ledge of coquina. Tucked into an overhang of ferns and shrubs, the top layers of fresh coquina are peachy to orangish tan, a result of oxidation of iron in the stone. Most of the wall is the more typical tan, which subsequently bleaches out in the sun to the gray of the castillo.

  The drab colors of coquina, the stone, fail to convey the beauty of coquina, the clam
. As the specific name, variablis, implies, no two look alike. Never uniform and always complex, the colors can be banded, like growth rings, fingered, like rays of sunlight, or both. Set against a yellow, ivory, or white background, rays and bands can be yellow to russet, blue to purple, pink, gray, or any mixture of these shades. Such variation has led to common names of butterfly shell and periwinkle.

  The Donax’s kaleidoscope of pattern and color helps make the clams less visible to predators, such as oystercatchers, sanderlings, and ghost crabs. One way to locate coquina clams is to look for groups of birds probing the sand to find the buried bivalves. Less mobile predators include moon snails, which nab Donax with a lightning dart of their foot, and lettered olive snails, which latch onto a coquina and pull it under the sand for a subsurface snack. Fish also eat coquinas or at least have the “nasty habit of biting off the siphons,” says marine biologist Olaf Ellers.19 Coquinas have two siphons: one for sucking in food, the other for expelling waste.

  People also eat coquina clams. The earliest evidence of people inhabiting what is now Florida comes from coquina shell middens fifty-seven hundred years old. Ancient beach dwellers appear to have eaten coquina clams seasonally for thousands of years. Archaeologists don’t know exactly how prehistoric people ate coquinas, but modern molluskivores prefer a broth, which writer Marjorie Kinnan Rawlings describes as delicate and delicious.20 She recommends serving it piping hot with “two tablespoons thin cream and a small lump of butter.”

  At the quarry, away from the prying eyes of law-abiding, law-enforcing national park rangers, you can run your hand over the coquina. Shells will spill out and cascade down the slope. In some layers, roots poke out, having penetrated over a foot deep. They look as if they would slice through the rock if you pulled on them. How could anyone think this clammy material would be good for building, particularly for a fort to protect a town from rampaging pirates and overzealous Englishmen?

  Known officially as the Anastasia Formation, the 110,000-year-old layers of coquina outcrop as a wisp along the east coast of Florida from Anastasia Island south to Boca Raton. Stretching for 225 miles, the rock formation is never wider than 10 miles and seldom thicker than six feet, although some beds are up to fifty feet thick.21 Made primarily of shells, shell fragments, and quartz sand, the Anastasia can be seen at Marineland, Flagler Beach, Blowing Rocks Preserve, and House of Refuge (in Martin County).

  Close-up of coquina showing shells.

  Coquina is geology in its most elemental form: not quite rock and not just a pile of shells, more a stone during its gestation. It is sort of the geologic opposite of Morton Gneiss. Every species found in the Anastasia can still be found living on beaches in Florida. No life existed on Earth when the gneiss formed. In the gneiss you can see how billions of years of geologic processes have melted, mixed, and metamorphosed the rock, whereas the coquina doesn’t appear that different from the day it first formed. Look at gneiss and you can tell it is very hard rock. Touch coquina and you can feel that it is very soft rock. Part of the appeal of coquina, at least to a modern visitor, is its elemental simplicity. You can easily understand how a stone forms.

  Imagine a beach, any beach where clams and cockles and scallops and crabs live. They die. In places, the currents sort the remains into homogenous piles of small clamshells. In other locales water mixes the shells into heterogeneous heaps. Time passes. Rainwater washes down into the piles and dissolves away the calcium carbonate that makes up the shells. Gravity pulls the water down into the pile. The water becomes saturated and begins to deposit minute crystals of calcium carbonate on any surface the water touches. The crystals cement the shells together and coquina is born.

  The new coquina changes little for hundreds of thousands of years, but if we peer into the future, we would eventually see new materials, such as sand, silt, and even more shells, beginning to accumulate on the coquina. The weight would compress the layers, which would become denser. More cement would accumulate and after millions of years, the coquina would now look like a rock, solid and hard. You would still recognize the fossils but no original calcium carbonate would remain. The coquina would now be a true limestone.

  In the Anastasia, cementation, or lithification, was aided by the Donax shells. Like most bivalves, Donax shells are made from calcium carbonate, but not the usual form of calcium carbonate, called calcite. Instead, Donax are made from aragonite, a less stable form of calcium carbonate. If Donax had been made from calcite, rainwater would not have been able to dissolve the calcium carbonate as quickly, and the shells may not have been cemented together into coquina. The Spanish might not have retained Florida and life as we know it may have been completely altered. Fortunately the clam was there.

  Donax clams also affect coquina after the stone has been quarried. In contrast to how brownstone seasons—by internal water transporting minerals to the stone’s exterior where calcite and silica reprecipitate on the surface—coquina hardens through external water, either rain or runoff, dissolving aragonite and precipitating cement near the surface. In both cases, seasoning creates a harder shell, sort of like chocolate coating on an ice cream bar.22

  Lithification occurred and still occurs very rapidly in the Anastasia Formation. South around Cape Canaveral, perfectly preserved ghost crabs, which died in their burrows, have been frozen into the coquina. They look like some twisted version of Shake ’N Bake with grains of sand, shell bits, and calcite coating the crab carapace.23 Closer to St. Augustine, lithification has locked Coke bottles in place.

  Deposition of the Anastasia occurred in a high-energy, shallow marine environment. Specifically, the coquina accumulated in the swash zone, the area along a beach intermittently covered and uncovered by waves. If you think about any swash zone you have seen, you will realize that it is a harsh environment, with waves constantly pounding and abrading the beach, which helps explain the abundance of shell fragments. And because of currents and storms depositing sediments, layers of nearly pure sand periodically interrupt the layers of shells, which created the zones of weakness that quarry workers exploited in order to split the coquina into blocks.

  The swash zone is an ideal habitat for coquina clams, says Olaf Ellers, who wrote his Ph.D. dissertation on the mollusk’s migratory movements. Winter finds Donax offshore in deeper and safer water, away from predators. During warmer months, they follow daily tides, moving inland with a rising sea and seaward as the water retreats. Their goal is to situate themselves in the swash zone where moving water suspends food particles. Once they reach their ideal location they use their shovel-like foot to dig themselves into the sand. Bad weather doesn’t stop coquinas from their travels, as Ellers found out when he snuck into a hurricane zone while working on his dissertation and watched coquina battle the big waves. I don’t recommend following Ellers’s lead.

  To facilitate movement, coquinas pump their foot up and down like a pogo stick to leap into the surf. Ellers coined the term “swash-riding” to describe this molluscan leaping and surfing. Like their human counterparts, coquinas are picky about their waves. “They choose only the 20 percent of waves that would carry them the furthest distance shoreward,” he says.

  Ellers further discovered that they detect which waves to surf by feeling sound vibrations generated by the crashing waves. “It’s analogous to the vibrations you feel when a large truck passes,” he says. “Larger waves produce more vibrations.” The coquina are so in tune with these sounds that Ellers learned to play a trick with them. In his lab, he would fill a bucket with bivalves and impress his friends by playing a sound and getting all of the clams to jump.24 Conchologists must be an easy group to impress.

  When the Anastasia formed 110,000 years ago, Earth was in what is known as an interglacial period, one of a number that have occurred during the past 2 million years. We are in an interglacial at present, meaning that the planet is between ice ages, the last of which ended about thirteen thousand years ago. The big difference is that during Anastasia times, the
climate was warmer than it is at present, which melted more of the planet’s glaciers and made sea level as much as twenty-five feet higher than it is today.

  As temperatures cooled during the ice age following the Anastasia interglacial, sea level began to fall, eventually dropping three hundred feet below modern sea level during the last ice age, as the glaciers tied up water that normally would have been in the oceans. Falling sea levels stranded the recently deposited shells far inland. Freshwater soon mixed into the deposit and began to cement the shells. The Anastasia Formation was born.

  In 1596 it became the first building stone used by European colonists in what would become the United States. The Spanish used coquina to erect a powder magazine, a building that housed gunpowder, in fort number eight.25 The oldest extant coquina structure is a well, built around 1614. Nothing else appears to have been built from coquina until the castillo.

  What makes coquina more remarkable is where it outcrops. If Pedro Menéndez de Avilés had decided to establish his base of operations north of St. Augustine in 1565, his late-seventeenth-century followers would have been in trouble. No good port with access to freshwater and good building stone occurs along the coasts of Georgia, South Carolina, or North Carolina. Serendipitously,Menéndez had chosen the one harbor with good stone. Without those Donax clams, who knows what would have happened to the Spanish?

  “The castillo was a fantastic deterrent. Anyone sailing by sees this little harbor, little town, and great big hulking white and red fortification, immediately knows this is a Spanish fort with lots of guns,” said Joe Brehm. “It says, ‘Don’t mess with us or we will hurt you.’ ”

  The design was not unique. After Ignacio Daza surveyed the site, he pulled out his military engineering books, which contained a catalog of designs, and “literally found a fortification that would fit his needs but scaled it down,” said Brehm. “The castillo is essentially a one-fifth scale model of what was known as a ‘frontier fortification.’ If you looked at a map of Paris and the surrounding area in the seventeenth century, you would find at least seven forts that look just like this one.”