Unearthing Mineral Wealth in SE GA
In the world of chemical elements, Titanium (Ti) and Zirconium (Zr) stand for strength and durability, which is why they are critically important for manufacturing consumer and industrial products, from paint to airplanes to artificial hip joints. Sands containing titanium and zirconium minerals are the most important source of the two elements. Mineral sand deposits are scattered throughout the world. Southeast Georgia and northeast Florida are blessed with this important resource.
Georgia’s mineral sand deposits are ancient barrier island sediments that formed over the past million years when sea levels receded. The former islands are now pine-covered sand ridges that step down from Charlton County to today’s Atlantic Ocean shoreline. SIM’s modern mining technology pinpoints the valuable minerals buried in the ground, extracts them, and then returns the land to the same condition as before the mining began.
Here’s how SIM finds, extracts and processes titanium and zirconium mineral sands at its South Georgia operations:
AT THE MINE
- Locate and assay – A drill rig collects samples of the sandy sediments from many locations in an area of interest. The samples are examined in the field by SIM geologists and then sent to our laboratory for precise determination of the quantity and type of minerals in the sand.
- Environmental screening – A crucial step in assessing whether a site can be mined is to conduct field surveys to identify sensitive environmental resources such as streams, wetlands, rare plants and animals, exceptional natural habitat, and archeological remains. SIM’s mine planning attempts to avoid and minimize impacts to sensitive resources. We work with University of Georgia scientists to relocate gopher tortoises identified during this preliminary phase.
- Site preparation – SIM leases the mineral rights from private landowners, most of whom are using the land for commercial timber growing. In advance of mining, erosion and sedimentation control measures are installed, the timber is harvested, and the topsoil is removed and stockpiled.
- Excavation and screening – An excavator digs up the sand underneath the topsoil and loads it into trucks. The trucks haul the sand and dump it at the ore stockpile. The sand ore is conveyed into a rotating screen that rejects roots and chunks of hardpan. The sand falls through the screen into a sump where it is mixed with water and then piped to the wet mill.
- Heavy mineral sand separation – Most of the excavated sand is quartz that has no commercial value. The wet mill at the mine separates the valuable titanium and zirconium mineral sands from the un-useable quartz sand. The sand-water slurry piped from the rotating screen is pumped to the top of the wet mill where it flows down a series of spirals, resembling miniature water slides. Because the titanium and zirconium mineral sand grains are twice as heavy as the quartz sand grains, they move down along the inner edge of the spirals while the lighter quartz flows down along the outer edge. Gates and slots in the spirals collect the heavier titanium and zirconium minerals and send them to a stockpile for transport offsite at the mineral sand plant. The quartz sand passes down the spirals to a tails sump. The sand tails are pumped and discharged into the mine pit excavated the previous month.
AT THE MINERAL SEPARATION PLANT
- Mineral sand processing – Heavy mineral sand that was separated at the mine must be further processed to produce individual mineral sand products:
- Gravity – Heavy mineral sands are mixed with water and pumped through a “classifier” where the flow of the water washes away the remaining lighter minerals.
- Drying and heating - Water is sucked out of the heavy mineral sands on a vacuum screen. Then the sand is conveyed to the primary dryer where the remaining moisture is evaporated and the sand is heated.
- Electrostatic and magnetic separation – An electrical charge is applied to the heated sand and the sands pass over an oppositely charged roller. The titanium minerals are conductive and fly off the roll to a bin. Zircon and other minerals that are non-conductors stick to the roller and are brushed off into another bin. The conductors (titanium minerals) then go through a series of magnets and additional electrostatic processes to produce rutile (TiO2), ilmenite (FeTiO3), and leucoxene (weathered ilmenite that has less iron) sand products. The zircon (ZrSiO4) and some other nonconductive heavy minerals are returned to the wet circuit for additional gravity separation, dried again, and subjected to electrostatic and magnetic separation to produce the zircon sand product.
- Shipping – the mineral sand products, stored in bins, are conveyed to a truck and rail loading facility. Most mineral sands are shipped by rail to industrial customers around the United States.
SIM employs a continuous reclamation process to reduce the mine’s footprint, quickly return the land to productive use after mining, and minimize the disruption of the owner’s use of the land. The mine continually advances in a sequence where one area is cleared for mining, another area is actively mined, and a third area that was recently mined is being reclaimed. Because the wet mill removes only about 2 percent of the sand, our mining process generally restores the land to its pre-mine elevations. Ponds and lakes are created only when the landowner requests those changes.
- Refilling the pits – The quartz sand excavated from the active pit and rejected by the wet mill is discharged into the previously mined pit. As the active pit is excavated, the sand tails fill up the previous pit. When the pit is refilled, it is graded and the stockpiled topsoil is spread on the surface.
- Planting – The topsoil contains viable roots and seeds that quickly re-sprout so that planting a cover crop is unnecessary. Most landowners request that SIM plant pine trees on the replaced surface.
- Release – After two growing seasons, the reclaimed areas host a lush understory and healthy pine seedlings. At this time, the land can be released from the Surface Mining Permit that allows the state to regulate active mining sites.
CLOSING THE LOOP: A Water Conservation Approach to Mining
While we are bringing these important minerals to market, SIM makes sure that another valued natural resource - water - is treated with equal care.
Water is needed to pump the sand around the mine and to separate the valuable titanium and zirconium minerals from the other sand. The water used in the mining cycle is obtained by pumping out the water that seeps into the active pit. The pit water is mixed with the sand ore and then, after the heavier minerals are separated, the lighter quartz sand “tails” are pumped back to a previously mined pit and discharged. In this way, the water that comes out of one pit goes right back into another pit nearby, so that the water is continually used, reused, and recycled. SIM is a conservative user, carefully managing the amount of water we access. No chemicals are used to separate the mineral sands except for water treatment agents that clarify the water used at the wet mill.
We apply the same water conservation principles at the Mineral Sand Plant. Water obtained from a well is continually reused, recycled, and returned to our process water reservoir. Only a small amount of process water is clarified and discharged.
Mining and Reclamation Cycle
At SIM's mine site, small areas are mined then reclaimed quickly and efficiently, so that valuable minerals are extracted with minimal impact, and landowners get the use of their land back in short order. Here's how it works:
1. Timber is cleared and topsoil is removed and stored nearby.
2. Sand is excavated from the pit. The heavier minerals are separated from the lighter minerals at the wet mill. Lighter sand is returned to the pit while the heavy mineral sand concentrate is trucked to the mineral separation plant for further processing.
3. Only about 2% of the sand is removed permanently. The lighter sand tails refill the previously mined pit (usually within one month), then it's graded to pre-mine contours. Topsoil is replaced, and pine trees replanted. The replaced topsoil provides viable seed and root stock for native understory species as well as soil nutrients and microbes needed by the pine seedlings.