PAUL ROUPE/209 Business Journal
High quality gypsum, like what is pictured here, is primarily used in farming as a fertilizer and soil additive.

Just off the eastern coast of Baja California, the island of San Marcos contains vast reserves of the mineral gypsum, which is blasted from natural deposits and shipped to—among many other locales–the Port of Stockton.

The purity of the gypsum on San Marcos, as well as neighboring Santa Rosalia about 15 miles away on the mainland, is the primary reason it is sought after. The mineral purity varies a few degrees between 90 and 95 percent, but that number is one of the highest anywhere in the world. For a bit of comparison, there is some gypsum naturally deposited in Bakersfield, but that only runs as high as 48 percent.

While the purest gypsum is used to make wallboard (drywall), the rest (but still very high quality) is used primarily for farming as a fertilizer and soil additive, and the benefits it provides are numerous.

The finer the gypsum is ground up, the easier it is to help break down hard soil. G-soil, one brand of these mineral-infused granules, assists in root growth, improves water retention in sandy soils, and helps combat plant diseases by increasing soil aeration.

But the gypsum takes a long journey to get to Central Valley Ag Grinding in Stockton.

There are two major miners of gypsum in Mexico—the Caopas Company, which operates out of Santa Rosalia on the Baja peninsula, and Comsa, on San Marcos. After the deposits are blown up off the mining site, a shelf is made, and the mineral is carved out of that shelf.

Once the enormous boulders are broken down into smaller rocks (size varies from six inches to very fine), they are ready to be loaded onto a vessel.

Typically, one of these shipments contains 40,000 metric tons. There is no regularity with which it arrives in Stockton because it runs on a supply and demand basis. When it does get here, it is offloaded as quickly as possible. The gypsum travels on a belt which spits it out onto a gigantic kidney-shaped pile, and it usually takes about 30 hours to get it all off of the vessel.

Once it is all in one spot, the trucks come in to take it back to be grinded. This is where the serious labor comes in, and Scott Baker, the trans-load manager for CVAG, makes sure his team gets the job done.

The trucks can handle about 25 tons each, and even if your math skills are rudimentary, you can figure that it takes about 1,700 trucks to pick up the entire shipment and send it from the dock to the grinding site.

Baker says that he and his team can shuttle it all out in about 16 to 20 days, but it takes almost two months to grind it all out and have it ready for delivery.

That’s a lot of gypsum, but the demand right now is high, and it’s vital to the Valley’s production.

“It’s very important in the Central Valley area,” Baker said. “Every vineyard and orchard and field needs to have this.”

With the gypsum now at the grinding site, the process needs a few more steps before it’s ready to be shipped out.

There are feed hoppers and screens and crushing machines and the site itself looks like some sort of industrial wasteland. Mountains of the powdery mineral loom behind mechanical arms and belts, and the pulverized bone color of the Comsa gypsum sets a stark contrast against the brown/reddish hue of the Caopas’ brand.

There is a difference in price and quality between these two, but both are equally useful. (The minerals from nearby copper mines and other natural deposits in Baja California, as well as the presence of more iron, are responsible for this variance).

After it’s broken down for the first time, it must be screened again to make sure it’s fine enough.

“Our quality assurance process is we test all of the ore coming in for purity and consistency,” Baker says. “Then we test our crushed material to make sure we always meet our size specifications for application.”

In this case, anything under 1/8 of an inch is acceptable. If it doesn’t measure up, it’s sent through the crusher for another round.

Then a loader scoops up the gypsum and dumps it in the back of truck, and finally, it’s ready to be shipped in 80,000 pound loads. But that’s where CVGA’s job ends.

Rare Earth Organics is the primary owner of the gypsum that makes its way here, and it’s their responsibility to distribute it to the market. They are a part of Bronco Wine Company, who uses the final product as a boost for their vineyards.

The gypsum finds its way throughout the Valley and up north, from Chowchilla to Sacramento and Napa, where it will be ready to be applied in various ways. Some farmers use a drip system, and others use a machine behind a tractor that tosses out little granules as it combs the field. But the result is the same; a necessary soil supplement in an area where abundant and healthy crop production can mean the difference between a bad season and a bountiful harvest.