Gold doré bar

Dore gold bars are semi-pure gold bars produced during the initial stages of gold refining. They are typically cast from gold ore that has been mined but not yet fully refined. So gold doré refers to a bar composed of a mixture of precious metals, though these bars generally contain gold and silver. A doré bar is usually produced as part of the mining and refining process, but can also be created from scrap gold.

It is a very imprecise term that is applied to numerous forms of partially-refined gold. On average, a doré bar contains 50-75% pure gold. These bars require further refinement before the metal can be used as raw material for producing gold items. Gold doré bars are therefore neither ore nor bullion, but simply metal bars with a high gold content.

Pure gold is extremely malleable, and is usually mixed with other metals for jewellery and other items that need to be hard-wearing. Counter-intuitively, after a doré bar has been refined, the process is reversed – returning the alloy back to its pure state. This could then even be alloyed once more; however unlike doré bars, the resulting metal will be a precisely defined alloy with known metal characteristics.

Gold doré bars can be assayed for their gold content, and traded in a similar manner to bullion bars. The market is very small however, and generally limited to specialist dealers, refiners, and mints. This is because doré bars are not held to any specific standard and are different from refiner to refiner. Some of these bars can weigh as much as 25kg, and the purity can vary greatly. Gold doré bars also lack the necessary purity to be considered as investment gold.

Key Takeaway

Dore gold bars are semi-pure gold products with significant impurities, including silver, copper, and trace metals. They serve as an intermediate step in the gold refining process and are not as pure or uniform as refined gold bars. For precise impurity analysis, advanced techniques like fire assay, XRF, or ICP spectroscopy are used.

Dore Gold Bar Specifications

Composition

• Gold Content: Typically ranges between 50% to 90% gold, depending on the source ore and mining process.
• Impurities:
  • Silver (Ag): Often the second most abundant metal, ranging from 5% to 40%.
  • Copper (Cu): Commonly present, ranging from 1% to 10%.
  • Platinum Group Metals (PGMs): May include small amounts of platinum (Pt), palladium (Pd), and rhodium (Rh).
  • Base Metals: Such as iron (Fe), lead (Pb), zinc (Zn), and nickel (Ni), typically in trace amounts.
  • Other Elements: May include traces of mercury (Hg), arsenic (As), and antimony (Sb), depending on the ore source.

Physical Characteristics

• Shape: Usually rectangular or trapezoidal, but can vary depending on the casting process.
• Size: Common weights range from 5 kg to 25 kg, though larger bars may also be produced.
• Surface: Rough and uneven, often with visible impurities, slag, or oxidation layers.
• Color: Varies depending on the composition, often appearing dull yellow or greenish due to impurities like silver and copper.

Purity

• Dore gold bars are not fully refined, so their purity is lower than that of refined gold bars (e.g., 99.99% pure gold).
• The gold content is typically measured in karats or as a percentage (e.g., 70% gold).

Impurity Analysis

• Assay Methods: Impurities are analyzed using techniques such as:
  • Fire Assay: Traditional method for determining gold content.
  • X-Ray Fluorescence (XRF): Non-destructive method for analyzing metal composition.
  • Inductively Coupled Plasma (ICP) Spectroscopy: Used for precise measurement of trace elements.
• Typical Impurity Levels:
  • Silver: 5% to 40%
  • Copper: 1% to 10%
  • Platinum Group Metals: 0.1% to 2%
  • Base Metals: 0.1% to 5%

Markings

• Dore bars may bear basic markings such as:
  • Weight (in kilograms or troy ounces).
  • Assay results (gold content percentage).
  • Mine or refinery identification.
  • Batch or lot number.

Uses

• Dore gold bars are typically sent to refineries for further processing to produce high-purity gold bars (e.g., 99.99% pure).
• They are not traded on the open market like refined gold bars but are instead used as an intermediate product in the gold supply chain.

Gold doré making process

Production Key Points

• Produced directly from gold mines as part of the initial refining process.
• The bars are cast in molds after the gold ore is smelted.
• Smelting Process:
  • Ore is crushed and mixed with fluxes (e.g., borax) to remove impurities.
  • The mixture is heated in a furnace to separate gold and other metals from slag.
  • The molten metal is poured into molds to form dore bars.

The term gold doré is an embellishment of the French “doré” which literally translates as golden, gilt or gilded.

Gold doré bars commonly come from two sources; mines or reclamation scrap. Mines almost never excavate pure gold ore. Most ores contain a mixture of gold and other useful base and/or precious metals. Silver for example is one of the precious metals most often found with gold ore, so a doré bar will often be made primarily from these two metals.

For ease of transport it is common practice for mines to partially refine the ore they produce. This removes any waste materials which have no further value, while reducing the output to manageable compact bars. Any dirt, rocks, or cavities are removed, leaving a single lump of metal that is easier to handle for refineries.

The resulting amalgams are referred to as doré bars. These partially refined bars may contain a mixture of gold, silver and/or other base and precious metals.

Scrap metal gold doré bars are again produced to ease transport by saving space. Scrap metal with a high gold content is often crushed or melted to form doré bars ready for further refining. As an example, someone who buys scrap gold jewellery will melt the scrap into a single doré bar. If you imagine the wasted space in a ring or bracelet, it is easy to see the appeal in melting the items down.

• Gold doré is partially refined metal with a high gold content
• The majority of doré is produced by mines and metal recycling
• Gold doré bars generally contain 50 – 75% pure gold

Comparison with Refined Gold Bars

Ametheus gold doré

Our Purity: 95.787% or better after further processing.

Weight & Quality: Final quality and quantity shall be determined by an independent assay report of a government licensed refinery nominated by the Buyer (“the Refinery”) shall be used and accepted as final and absolute.

HSN Code: 71131990

Documents to be Provided by the Seller:

The Seller shall provide the following documents to the Buyer prior to arrival of Gold:

1. Two originals of Commercial Invoices.
2. One original Certificate of Origin.
3.  One Government assay report.
4. One copy of Airway bill marked “Airfreight Prepaid”.

Shipment:

We partner with globally renowned logistics providers specializing in the secure transportation of precious metals. Our shipments are handled by Brinks (brinksglobal.com) and Ferrari Group (ferrarigroup.net), ensuring superior security, reliability, and efficiency.

gks@ametheus.com