A tailing has different meanings depending on the field. In mining, tailings are the waste materials left over after valuable minerals have been extracted from ore. In laboratory chemistry, tailing describes a distorted peak shape on a chromatograph. And in fishing, tailing refers to a fish feeding in shallow water with its tail poking above the surface. Here’s what each one involves and why it matters.
Tailings in Mining
Mine tailings are pulverized rock mixed with water that remains after the valuable minerals have been separated out. When ore is pulled from the ground, it goes through physical and chemical processing to extract metals like gold, copper, or iron. Everything left behind, the crusite, sand-like slurry of ground-up rock particles and processing chemicals, is the tailings.
These aren’t just inert dirt. Copper tailings commonly contain arsenic, lead, cadmium, and uranium. Gold tailings often carry cyanide (used during the leaching process to dissolve gold from rock) and mercury. These heavy metals persist in the environment, don’t break down naturally, and accumulate up the food chain. When dissolved in water, they’re toxic to aquatic life and dangerous to nearby communities.
Tailings are typically stored in large engineered structures called tailings storage facilities, essentially dammed ponds or dry-stacked deposits that can cover hundreds of acres. When these facilities fail, the consequences can be catastrophic. The Global Industry Standard on Tailings Management, developed by an international review panel, now requires operators to maintain zero tolerance for human fatalities and strive for zero harm across a facility’s entire lifecycle, from design through closure. The standard includes 77 auditable requirements covering everything from monitoring systems to emergency response plans and public disclosure of facility information.
Reprocessing Old Tailings
Because extraction technology has improved over time, old tailings sometimes contain recoverable metals that earlier methods couldn’t capture. In theory, reprocessing these deposits could reduce environmental liabilities while contributing valuable materials. In practice, it rarely happens at scale. A review of U.S. Securities and Exchange Commission filings found that companies have only conducted large-scale tailings reprocessing at 27 sites, mostly for gold, and typically based on limited sampling. Only about a quarter of qualified mining professionals surveyed had even evaluated the feasibility of reprocessing. The barriers are practical: a successful project requires expertise spanning geology, mineral processing, economics, environmental science, and navigating complex regulatory frameworks all at once.
Peak Tailing in Chromatography
In analytical chemistry, tailing refers to a specific problem with peak shape on a chromatogram. Chromatography separates the components of a mixture by passing them through a column. Each component ideally shows up as a clean, symmetrical, bell-shaped peak on the readout. When a peak has tailing, its back edge drags out to the right instead of dropping off cleanly, making the peak look lopsided, like a bell with a long skirt trailing behind it.
This happens when some spots on the column’s surface hold onto a compound more strongly than others. Instead of all molecules of that compound passing through at the same speed, some get stuck slightly longer, arriving at the detector late and stretching the peak’s trailing edge. A perfectly symmetrical peak has an asymmetry factor of 1.0. Good columns produce peaks between 0.95 and 1.0.
Common Causes and Fixes
When every peak in a chromatogram tails, the problem is usually systemic: contamination building up at the column inlet, metal contamination in the system, a degraded column, or extra-column effects from tubing that’s too long or too wide between the injector, column, and detector. When only certain peaks tail, it’s more likely a chemical interaction, often between basic compounds in the sample and residual reactive sites on the column surface.
Solutions depend on the cause. Lowering the pH of the mobile phase reduces interactions with those reactive surface sites. In one documented example, dropping the pH from 7.0 to 3.0 improved peak symmetry from 2.35 to 1.33. Adding a competing compound to the mobile phase can also help by occupying those sticky surface sites before the sample compounds reach them, improving symmetry from 1.91 to 1.18 in one case. For contamination, reversing the column and flushing it with solvent or an acid wash can restore performance. If none of that works, the column needs replacing. On the hardware side, using shorter, narrower-bore tubing and a low-volume detector cell minimizes the extra-column effects that broaden and distort peaks.
Tailing in Fishing
In saltwater flats fishing, tailing describes a fish feeding in water so shallow that its tail breaks the surface. Species like bonefish, redfish, and permit do this when they tip downward to root along the bottom for crabs, shrimp, and other prey. The tail fin sticks up above the waterline, waving slowly as the fish forages.
For anglers, spotting a tailing fish is a prime opportunity. It signals a fish that’s actively feeding, focused on the bottom, and likely to strike a well-placed fly or lure. It also tells you exactly where the fish is and which direction it’s moving, which is valuable information on open, featureless flats where fish are otherwise hard to locate. Much of sight-fishing strategy on tropical and coastal flats revolves around scanning for these telltale tail tips catching the light above the surface.