Facebook YouTube Share Tiktok Linktree by Goldminingtips Admin How to Spot Fool’s Gold It is understandable for a gold prospector to celebrate finding rocks with a shiny appearance in their gold pan; thinking that they have found gold. Before celebrating your find, you should make sure that you have actually found real gold and not one of the rocks that are often mistaken for gold. In this blog, we explore some of the rocks that are often mistaken for to gold. We also provide some useful information to help you identify if you found a material that looks like gold but is not. Why Learn How to Identify Fool's Gold? Although some rocks / materials can be mistaken for gold due to their metallic appearance, if you know what to look for, and how to do proper tests, you shall be able to easily distinguish between fool's gold, and other worthless material, and gold. This shall allow you to co...
Facebook YouTube Share Tiktok Linktree
by Goldminingtips Admin
Gold's Geological Secrets and Where to Find It
While gold is widely distributed throughout the earth crust (on land and in the sea), it is a rare element with a concentration of 4 parts per billion.*
Despite it rarity, gold's unique characteristics - being both beautiful and very useful for various reasons - means it is a precious metal that has been mined and used by different peoples around the globe since the beginning of human history.
But how was this precious metal formed?
Beyond its glittering allure there are certain conditions that must be present for gold to form.
Understanding how gold forms and where it hides transforms prospecting from luck to science, thereby improving your chances of finding gold. In this blog, we shall unravel these secrets.
I. How Gold Forms in the Earth
Gold’s story begins not on Earth, but in the violent hearts of dying stars. Unlike lighter elements forged in stellar cores, gold requires cataclysmic energy to form:
- Supernova Nucleosynthesis: When massive stars explode as supernovae, extreme conditions fuse lighter elements into heavy metals like gold. Neutron star collisions, observed in 2017, also eject gold-rich debris into space.
- Earth’s Accretion: Gold arrived on Earth via asteroid bombardment during the planet’s early formation. While most gold sank into the core during Earth’s molten phase, trace amounts remained in the mantle and crust—averaging a mere 3 parts per billion.
On Earth, gold concentrates through geological drama:
1. Hydrothermal Fluids: Deep underground, superheated water (150–300°C) leaches gold from rocks. These fluids rise through cracks, cooling and depositing gold in quartz veins or sulfide minerals .
2. Magmatic Intrusions: Granite melts can carry gold upward. When these melts crystallize, gold concentrates in veins or contact zones (e.g., porphyry deposits) .
3. Metamorphic Rebirth: Mountain-building events (orogeny) squeeze rocks, releasing fluids that redistribute gold into shear zones. Western Qinling (China) and Egypt’s Eastern Desert exemplify this .
> Key Insight: Gold’s immobility under everyday conditions contrasts its surprising with the fact that is is mobile under certain conditions, such as in the Earth’s hot, mineral-rich fluid environments.
II. Lode vs. Placer Deposits: Where Gold Hides:
Gold deposits fall into two categories: primary (lodes) and secondary (placers). The type of deposits determines the approach and equipment a prospector shall use to locate and extract the precious metal.
A. Lode Gold:
- What It Is: Primary deposits are those deposits that form in situ within hard rock. Examples include gold veins (e.g., California’s "Mother Lode") or disseminated ores (e.g., Nevada’s Carlin Trend).
- Formation:
- Veins: Gold precipitates in fractures with quartz or sulfides (pyrite, arsenopyrite).
- Disseminated: Microscopic gold "invisibly" permeates sedimentary rock (Carlin-type).
- Key Features:
- In these type of deposits, the gold is locked in minerals. In order to release it, the minerals are often crushed to liberate the gold.
High purity (often >90% Au) but low grades (1–10 g/ton)
- Found in orogenic belts (e.g., Rockies, Alps) or ancient cratons (e.g., Western Australia).
- Mining (Extracting the gold): Requires capital-intensive methods: blasting, drilling, and chemical processing (cyanide leaching, flotation).
B. Placer Gold:
- What It Is: Weathered gold transported from lodes by water/gravity, then deposited in sediments.
- Formation Process:
1. Weather Erosion: Lodes exposed at the surface and due to weather conditions, the gold is released and transported to new places.
2. Transport: Rivers (and other waterways / sources) carry gold downstream. The weight and density of gold cause it to sink when it it is able to settle, concentrating in:
- River bends (inside curves)
- Bedrock cracks
- Gravel "pay streaks"
- Bench deposits (ancient, elevated river terraces)
- other places where gold gets lodged due to gravity.
- Key Features:
- Free-milling gold: Nuggets, flakes, or dust require no crushing.
- Lower purity (<90% Au) due to alloying/erosion.
- Accessible: Mined via panning, sluicing, dredging, trommels, wash plants.
Memorable Examples: Gold rushes, such as California’s Gold Rush in 1848 (750,000 lbs gold), and the largest nuggets ever found, such as Australia’s "Welcome Stranger" nugget (weighing 72 kg).
Ancient Placer Deposit: Australia’s "deep leads" are fossil riverbeds buried by lava flows, requiring underground mining of gravels.
Lode vs. Placer: A Comparison
Deposit Type |
Lode |
Placer |
|---|---|---|
| Form | Microscopic/nuggets in rock | Free particles in sediment, both small and larger pieces (nuggets) |
| Location | Bedrock veins, sulfide ores | Rivers (Waterways), beaches, glacial drift |
| Gold Purity | High (>90%) | Moderate (<90%) |
| Mining Method | Blasting, chemical processing | Panning, sluicing, wash plant, dredging |
| Economic Barrier | High ($millions) | Low (artisanal-friendly) |
| Global Production | ~60% of gold today | Declining (exhausted deposits) |
III. Prospecting Clues: Reading Nature’s Signposts
When searching for lode and / or placer gold deposits it is helpful to learn about the geology associated with gold and, in the case of the placer deposits, how gold is transported from it's source on its journey to where it settles on the earth's crust. Key indicators include:
- For Lodes:
- Iron-stained quartz veins (rusty colors signal sulfides).
- Hydrothermal alteration: These are changes occuring in rock formations upon interacting with hot fluids. Gold is known to be associated with bleached or clay-rich rocks near hydrothermal veins.
- Mineral associations: A range of minerals, depending on the environment. Mineral associations include: Quartz, Pyrite ("fool’s gold"), arsenopyrite, tellurides, copper, silver, and others.
- For Placers:
- Black sands: Magnetite/hematite layers in riverbeds trap gold.
- Ancient river terraces: Elevated "benches" indicate past flow paths / waterways where ancient placer deposit are formed.
- Coarse nuggets upstream: Size decreases downstream; the larger the nuggets, the closer it is likely to be to the lode, as gold is a heavy element.
IV. Why It Matters
Gold’s duality—lode versus placer—shapes economies:
- Placers enabled historic rushes (e.g., Klondike), democratizing wealth but most placer deposits have been exhausted and the remaining are depleting fast.
- Lodes dominate modern mining, yielding long-term, high-volume output but requiring significant investment to locate and extract.
- Tech’s Role: Satellites now map alteration zones for lodes; drones scan river sediments for placers.
Conclusion: The Alchemy of Geology
Gold’s journey—from stellar explosions to riverbeds—reveals Earth’s dynamic nature.
Whether you’re a beginner prospector, or a gold prospector with some experience of finding gold, knowing a little about the geology associated with gold, and how it is transported by nature, shall improve your prospects of finding your prize - placer or lode gold deposit.
Ready to Start Your Gold Prospecting Journey?
You'll find more resources to help you find more gold here:
* WC Butterman and Earle B Amey III, 'Mineral Commodity Profiles - Gold, US Geological Survey (2005)
Gold is found where it's been found before. With the right tools, equipment, and knowledge, you shall improve your prospects of finding the precious metal
Research Further:
- 'Gold', Geoscience Australia (May 2025) Available at: https://www.ga.gov.au/education/minerals-energy/australian-mineral-facts/gold.
Comments
Post a Comment