Types of Gold Ore

1. Free-Milling Gold Ore

This is the gold we all dream of. The kind that makes your life easy. Free-milling ore is what it says on the tin—the gold is mostly liberated, native metal. You can often see it sparkling in the quartz veins. It doesn’t play games with cyanide; it dissolves readily, giving you recovery rates that make you smile.

What you’ll see:

• Visible gold particles in quartz or oxide material.
• Low sulphide content—usually less than 1%.
• Responds beautifully to simple cyanidation.
• It’s straightforward and reliable.

How to process it (The Smart Way):
This is where you build a classic, robust, and efficient plant. You don’t need to overcomplicate it.

• خرد کننده: Start with a sturdy jaw crusher for primary breaking. Feed that into a cone crusher for secondary crushing. You want a consistent, manageable feed size for your mill.
• Grinding: A standard ball mill is your best friend here. Grind it to a fine sand (think 150-200 مش) to make sure any remaining locked particles are freed up.
• برای نوک: Don’t just run everything to leach tanks. Install a gravity circuit like a centrifugal concentrator right after grinding. This will catch those coarse, free particles immediately, boosting your overall recovery and preventing them from getting lost in the circuit.

2. Refractory Gold Ore

Ah, the tough nut to crack. If free-milling ore is an open book, refractory ore is a locked safe. The gold is there, but it’s finely disseminated and imprisoned inside sulphide minerals like pyrite or arsenopyrite. You can grind it to powder, and cyanide still can’t touch it. This stuff requires a sledgehammer approach.

What you’re dealing with:

• High sulphide content. It often looks like a brassy, hard rock.
• Gold assays might look good, but cyanide recovery is pathetic—sometimes below 50%.
• The gold is invisible; you won’t see it with a hand lens.

The Game Plan:
You need a two-step process: liberationthen oxidation.

• خرد کننده & Grinding: You still need a powerful jaw and سنگ شکن مخروطی setup. But the grinding is different. You need an ultra-fine grind. We’re talking SAG mills, ball mills, and often tertiary grinding with vertical mills or stirred mills to get the particle size down to 25-30 microns. You’re not just liberating gold; you’re liberating the sulphide grains themselves.
• The Key Step: Pre-oxidation. This is where you blast that sulphide lockbox open. You have three main choices: roasting (a classic method), pressure oxidation (POX in an autoclave), or bio-leaching (using bacteria). After this, the ore behaves like a free-milling ore and can be leached.

Table 1: Gold Ore Types At A Glance

3. Silver-Rich Gold Ore: The High-Maintenance Partner

This one’s a chemical variant. The gold isn’t pure; it’s naturally alloyed with silver, forming a mineral called electrum. While it’s still technically free-milling, the high silver content changes the chemistry of your leach circuit. Silver is greedy—it consumes more cyanide and oxygen, slowing everything down.

How to spot it:

• You’ll have high silver assays alongside your gold.
• Metallurgical tests will show slower leach kinetics and higher reagent costs.

Making it work:
The hardware up front is the same. The magic happens in the chemistry.

• Crushing/Grinding: Stick with your reliable jaw crusher, سنگ شکن مخروطی, and ball mill combo. The goal is the same: achieve a good liberation size.
• Leaching Adjustments: Your process engineers will need to tune the leach circuit. This means higher cyanide concentrations, better aeration, and possibly longer retention times in the tanks. Your equipment needs to be reliable to maintain a steady feed for this longer process.

4. Copper-Bearing Gold Ore: The Cyanide Killer

This one can be a real profit killer if you don’t handle it right. The gold ore type contains significant amounts of copper minerals—think chalcopyrite, azurite, or malachite (those green and blue minerals). The problem? Copper also dissolves in cyanide, and it does it faster than gold. It steals the cyanide, runs up your reagent bill, and creates nasty complexes that foul your carbon.

The tell-tale signs:

• Those distinctive green and blue streaks in the rock.
• Sky-high cyanide consumption and frustratingly low gold recovery.

Your strategic choice:
You typically have one smart path: flotation.

• Crushing/Grinding: You still need to crush and grind the ore (Jaw + Cone + کارخانه) to a size that liberates the minerals for separation (~150 microns).
• The Flotation Circuit: This is your essential add-on. You use flotation cells to create a copper-rich concentrate that contains your gold. You can then ship this concentrate to a smelter. This way, the copper pays for its own treatment, and you get credited for the gold. Trying to leach this ore directly is a losing battle.

5. Iron-Oxide Copper-Gold (IOCG): The Abrasive Giant

IOCG deposits are beasts. They are massive, incredibly hard, and brutally abrasive because they’re mostly made of magnetite and hematite. The gold and copper are sprinkled throughout. The number one challenge here is wear and tear. Your maintenance team will know all about this gold ore type.

What you’re up against:

• Rock that’s exceptionally hard and dense.
• Off-the-charts abrasiveness that will eat standard equipment liners for breakfast.

The equipment mindset:
You need a focus on durability and energy efficiency above all else.

• Primary Crushing: For big operations, a gyratory crusher is the only machine tough enough for the job.
• Secondary Crushing: Heavy-duty cone crushers with special, abrasion-resistant manganese liners are a must.
• Grinding Innovation: This is whereHigh-Pressure Grinding Rolls (HPGR) shine. Using an HPGR as a tertiary crushing stage before the ball mill is a game-changer. It’s more energy-efficient than additional crushing stages and creates micro-cracks in the ore, making the downstream grinding in your ball mill much easier. Everything in this circuit must be built for war.

6. Telluride Gold Ore: The Chemical Puzzle

This is a rare but fascinating find. اینجا, gold is chemically bonded with tellurium, forming minerals like calaverite. You can’t leach it because the cyanide can’t break that chemical bond. It needs a chemical “key.”

Identification:

• It often has a reddish-yellow tinge.
• Standard cyanidation tests will fail miserably.

The solution:
You have to break the bond first.

• Step 1: Fine Grinding. Standard crushing and ball milling to liberate the telluride minerals.
• Step 2: Roasting. The most common solution. You roast the finely ground ore, which oxidizes the tellurides and releases the gold. After roasting, the material can be leached like a normal free-milling ore.

7. Placer Gold: The Easy Streamer

Let’s change pace completely. Placer gold isn’t a rock; it’s gold that’s already been freed by nature and deposited in riverbeds and sands. There’s no crushing needed. The gold is already loose!

The good life:

• Liberated nuggets, flakes, and dust mixed in with sand and gravel.
• Processing is 100% physical.

The equipment list (no mills here!):

• You need a scrubber or trommel to break up clays and wash the material.
• Screens to size it.
• A series of gravity units—sluices, jigs, and especially centrifugal concentrators—to separate the heavy gold from the light sand. It’s all about moving volume and capturing gravity.