Aragonite, pure calcium carbonate pellets, called oolites (egg stones) by geologists, each the size of a pinhead, is mined in the Bahamas. It is very pure, light tan or buff in color, has no particles in it larger than a quarter, is durable, and causes no adverse effects on tourists, ecology or beach maintenance equipment.
As water warms, it drives out dissolved gases and in this case, the important gas is carbon dioxide. As it is driven out of the water, the ocean buffering system tries to maintain the status quo by breaking down bicarbonate ions in the sea and producing more CO2 and carbonate ions. The latter combine with calcium in solution in the water and form calcium carbonate, which crystallizes out in tiny spherical or ellipsoidal particles about as big as a pin head. These fall to the bottom and make thick deposits of beautiful sand.
It is an ideal material for beach renourishment except that we do not presently have any good way to get it from a large ship, in 40 feet of water, to the beach about half a mile away. When and if, we develop a good pumping system to do this, economically, we can hopefully restore our beaches without worrying about damage to the reefs offshore, and with much less concern about silt suspended along the shore.
When the aragonite is mined it runs thru a spider barge, where the water and aragonite go thru a grizzley (a shaker screening device). It takes out all the large particles, like conch shells, and most of the silt and very fine sand sized aragonite. What’s left is excellent beach material.
Anyone flying over the Bahama Banks knows about the sand waves that look like underwater sand dunes These are mostly aragonite. From Bimini to Ocean Cay. and east to Chub Cay and Andros, a large part of the Banks are covered with aragonite, in the form of oolites. There appears to be no shortage. The resource is in billions of tons.
In the past the same process occurred on the Florida platform and we got the Miami Oolite, a geologic formation, now turned to rock, that is common in southeast Florida. It is probably that some oolites are forming in Florida Bay today.
This very pure calcium carbonate is used for agricultural lime on farms where the soil is acid because of fertilizers, pine needles etc. It is spread like fertilizer and “sweetens” the soil. It is also an important ingredient in Portland cement, which is made by burning aragonite (or other calcium carbonate) in giant kilns with shale rock. The clinkers formed are cooled and ground up to make cement. It is an important in glass manufacture. Quarts sand (sugar sand), aragonite and soda ash are melted together to form glass. Aragonite is also used to knock down sulfurous gases in power plants, where it is converted to calcium sulfate or gypsum. The fines are sometimes used as extenders in linoleum manufacture, in place of more expensive plastics, etc.
Aragonite is no longer in big demand for several of these uses. We can buy cement from Mexico cheaper than the cost of importing the same amount of aragonite; before making cement of it. Recycling of glass has knocked the bottom out of glass manufacture and the same cost problem is found here. It turns out that other sources of aragonite or of calcite, another mineral with the same formula and most of the same uses, are more economical. Interestingly enough, one of these sources is in S Florida where we mine and ship millions of tons of ancient coral reef and sea bottom to the north every year. Many times I’ve waited for hundred car trains of limestone headed north.
Hopefully, we devise a way to get some aragonite from the boat to the shore. Bahama aragonite makes beautiful, environmentally desirable South Florida beaches in the few cases where it has been tried. The biggest holdups are “Buy American” and the cost of mining and delivering it to S Florida, which is still significantly higher than beach renourishment from nearshore borrow pits.
The name, by the way, comes from Aragon, in Spain, where it was first described, but not as oolites.
New information. Steve Higgins tells me that the environmental nit-pickers are worried about bringing foreign species to Florida in aragonite shipments. I told them that the Gulf Stream laves both Florida and the Bahamas. The Stream delivers the same organisms to both areas. I believe it is a specious argument! The Buy American has been modified for non-American materials where major advantages accrue for their use. I believe this is the case here.
Aragonite is generally coarser than SE Florida beach sand so will resist movement offshore, in winter, better. It is uniform in size and a very pleasant buff color; far better than gray sand from offshore borrow areas. The fines have mostly been washed out in the Bahamas when it is run thru a spider barge, sieving out conch shells and running the fines over the side with wash water.
Dredging companies and others have argued that it will impact turtle nesting. Turtles nest very well all over the Bahamas, on Ocean Key which is made up of pumped aragonite and on Fxxxx Key near Miami which was built years ago of aragonite.
They also complain that Phragmatopoma sp, the wormrock tube worms, would not build on it. This is bunkum too since I made an extensive search of the literature and found P. sp building tubes from all kinds of sand, glass beads, tiny particles of feces, etc. They are opportunists and build on whatever is available.
Since SE Florida (Dade, Broward and Palm Beach Counties) is talking of using tens of millions of cubic yards of aragonite, it is not at all unlikely that a very good price could be negotiated, delivered to the offshore pumping station.
There are reports that the Minister of Tourism has said they will never sell aragonite to Florida. We are talking about hundreds of millions of dollars for the Bahamas and work for more than 100 Bahamians. I worked as a consultant for Marcona, at the time the company running the operation. Part of the time they barged aragonite across the Gulf Stream and, as a matter of fact, the tug they used is now the “Berry Patch” artificial reef off Hillsboro Beach. I do not believe that a business proposition like this would be turned down, particularly since it would not impact Bahamas tourism, for the dredge site is on the Banks east of Ocean Key.
We are too late for this dredging cycle but perhaps the next one! Aragonite is cleaner (little or no silt), larger grained (less offshore transport in winter), available in millions of cubic yards, beautifully colored, and if imported, has little environmental; effect on our fragile ecosystem.