Land isn't uniform. Different materials settle in different places—and a little strategy before you dig can change what your sample has to say.

Here's a look at how soil tends to behave, and where the interesting stuff usually ends up.

Universal Hot Spots

Nature does most of the sorting work for you. Gravity, water, and time tend to drop their cargo in predictable places.

1. The lowest part of your property. Rainwater carries soil and minerals downhill. Whatever's been drifting around up top often ends up down here.
2. Natural drainage paths. Small channels where rainwater runs during storms—even if they're dry most of the year. These are highways for loose material.
3. Creek beds and seasonal streams. If you've got a creek, ditch, or stream that only runs in the spring, the sediment there is often a mix of everything upstream.
4. The base of slopes and hills. Heavy minerals creep downhill over decades. The bottom of a slope is where they tend to pile up.
5. Exposed rock or gravel patches. Where the topsoil is thin or gone, you may be closer to what the ground is actually made of.
6. Soil that looks different. Odd colors, dark sand, reddish dirt, unusually heavy-looking grains—these are clues.
7. Old disturbed ground. Places where the soil's been dug, graded, or piled up (old road cuts, construction scars, excavations) can expose layers that usually stay buried.

These patterns hold for almost anything that ends up in soil. The category-specific notes below build on top—not in place—of them.

Know What You're After?

Precious Metals

Precious metals are heavy. Really heavy. Which is great news for samplers, because heavy stuff generally follows predictable rules—it sinks, it settles, and it shows up where water slows down.

Beyond the universal patterns above, a few specifics:

• Inside bends of streams. When a creek curves, the water slows on the inside of the bend. Heavy stuff may drop out right there.
• Behind large rocks in streams. Big rocks can be natural speed bumps. Sediment may pile up in the slack water right behind them.
• Near quartz veins or white rock. Many gold-bearing areas are associated with quartz-rich geology. Soil near exposed white or glassy rock may carry traces of what the surrounding rock holds.
• Dark or "black sand" patches. Heavy, dark, gritty sand in a streambed or low spot often travels with precious metals. Black sand and precious metals frequently end up in the same places.
• Old mining areas or historical digs. If your region has any history of mining or prospecting, soil near those old sites may still carry overlooked material.

Rare Earth Elements

Rare earth elements generally don't look like anything. They tend to hide inside other minerals, so hunting for them directly isn't the norm. Instead, people often hunt for the kinds of soil that tend to hold them.

The universal patterns above apply. A few more worth knowing:

• Dark or "black sand" patches. Same as precious metals—heavy, dark sands often carry rare earth elements along for the ride.
• Near granite-like rock. Granite and similar rocks break down over time, and their mineral grains can hold rare earths. Soil near exposed granite outcrops may carry those broken-down minerals.
• Gravel bars and sandy deposits. Coarse material left behind by water tends to concentrate heavier minerals.
• Unusually colored soil grains. Dark, reddish, or heavy-looking mineral specks in otherwise normal soil could be a sign of rare earth elements.
• Rock piles and road cuts. Anywhere the ground has been broken open to expose deeper layers.

Crude Oil

Crude oil forms deep underground, but tiny amounts can migrate upward through rock and soil. A sample is useful because many times, this migration upward is undetectable with the human eye.

The universal patterns apply. A few more worth knowing:

• Springs, seeps, and consistently wet spots. Areas that stay damp even in dry weather may bring subsurface fluids closer to the surface.
• Along rock fractures or exposed bedrock. Cracks in rock can be natural pathways. If you've got cliffs, exposed stone, or rocky hillsides, soil nearby may carry trace hydrocarbons.
• Above clay-rich layers. Clay can act like a lid, trapping things underneath it. Soil just above a clay layer sometimes catches what tried to move up.
• Regions with oil and gas history. If there's been drilling, production, or known oil fields anywhere in your area—past or present—trace hydrocarbons may show up in soil even without surface signs.
• High and low ground tell different stories. Hydrocarbons can move in weird ways underground. A high point and a low point on the same property can have very different readings, so sampling both a high point and a low point can give you more to compare.

Heavy Metals

Heavy metals have a story. Some are natural to the ground beneath you. Others show up because of what happened on the land decades ago—old paint, leaded gasoline, farm chemicals, treated lumber, burned trash. The soil tends to remember.

Beyond the universal patterns above, here's where that history tends to show up:

• Near older homes or painted structures. Houses, barns, or fences built before the late 1970s may have lost exterior paint into the soil around them—especially within a few feet of walls and along drip lines where rain would carry paint dust down.
• Along older roads or driveways. Decades of leaded gasoline could have left their mark in the soil near roads. The first 10–20 feet from an older road tends to be where it shows up.
• Near pressure-treated wood. Older decks, fences, and playground structures were often treated with chemicals containing arsenic and copper. Soil right next to these can carry residues.
• Old burn piles and ash dumps. Burning trash can concentrate metals in the ash left behind. Soil where household garbage, wood, or debris was historically burned often carries traces.
• Around old workshops, garages, or equipment storage. Places where vehicles or machinery were worked on can carry residues from fluids, batteries, and parts.
• Old orchards and farmed ground. Pesticides and herbicides used on farms and orchards decades ago sometimes contained lead or arsenic. Those metals don't break down—they tend to linger.
• Near former industrial sites, mines, or rail yards. If your property is downwind or downhill from any of these, the soil nearby may have picked something up over the years.

Petroleum Contaminants

Petroleum contamination usually comes from a specific source like a spill, a leak, a tank, or a stored fuel can. It tends to spread downhill and downward, following gravity and rainwater.

The universal patterns apply, and these spots are most likely to tell a petroleum story:

• Old heating oil tank locations. Many old homes had above-ground or buried heating oil tanks. Soil around the old tank footprint—especially downhill from it—is where residues tend to settle.
• Garages, workshops, and sheds. Anywhere vehicles or equipment got worked on can carry traces of motor oil, fuel, or solvents.
• Driveways, parking pads, and long-term vehicle storage. Places where cars or trucks sat for years could have accumulated leaked fluids in the soil alongside and underneath.
• Fuel storage areas. If diesel tanks, gas cans, or generators were stored in one spot for a while, the soil there may carry residues.
• Downhill from any of the above. Petroleum often moves with rainwater, so soil downhill from a suspected source can pick up what migrated.
• Around farm equipment or machinery storage. Properties that stored tractors, heavy equipment, or fuel drums may have diesel or hydraulic fluid in the nearby ground.
• Old burn pits and dumping areas. Some properties historically got rid of waste oil by burning or pouring it out. Those spots may hold onto it.

A Few Things to Keep in Mind

UNDR analyzes the specific sample you send us—not your whole property. Two samples from the same acre can look completely different, and that's normal. One sample is one snapshot; another spot on the same land may tell a different story.

Also worth saying: Sampling in any of the areas described above does not guarantee any specific outcome. A finding in your sample is only a finding in your specific sample. It's a starting point for curiosity, not a final verdict on your land, your health, or your home's value. A professional is the right next step if a result raises questions you want to act on.

Happy hunting.

Important—Disclaimer About This Guide

The information in this section is offered solely for general educational and informational purposes. Any suggestion about where to sample, what kinds of locations may be worth exploring, or how soil and minerals tend to behave is general in nature and should not be construed as professional advice, recommendations, endorsements, regulatory guidance, or a substitute for consultation with qualified professionals. Sampling in any of the locations described above does not guarantee any particular result, finding, or outcome. Soil composition varies widely from spot to spot, and the suggestions here reflect general patterns—not predictions about your specific property. Before taking any action based on where or how you sample—including digging on property you do not own, disturbing protected land, sampling near structures or utilities, or acting on anything a sample reveals—you must consult qualified licensed professionals (including licensed geologists, environmental consultants, attorneys, surveyors, utility locators, and appropriate federal, state, and local authorities as applicable). Always call 811 or your local equivalent before digging. Any decision you make about where to sample, how to sample, or what to do with your results is your own, based on your independent judgment and the advice of qualified professionals you engage. See the full Master Disclaimer at www.undrco.com/disclaimer.