Physical Consistency
Assess whether measured mass and volume produce a density consistent with the stated physical question.
Gold Authentication Method
Gold Density & Hydrostatic Testing
Physical Verification of Suitable Gold & Precious-Metal Items
Density testing compares an item's measured mass with its measured volume. Hydrostatic weighing can determine volume through buoyancy under controlled conditions.
The result provides supporting physical evidence for a suitable solid item, not a definitive assay of exact gold fineness.
Bilex reviews the item's form, surface and practical suitability before confirming the examination approach.
Bilex Sample Handling
What Density Testing Measures
Density is mass divided by volume. For a suitable solid item, mass can be measured directly while volume may be determined from dimensions or by hydrostatic weighing, which uses the change in apparent weight when the item is immersed under controlled conditions.
The calculated density can be compared with relevant physical expectations and with other evidence about the item. The examination is normally non-destructive when the specimen is physically suitable for weighing and immersion.
Density testing alone cannot establish exact gold fineness. Different alloy compositions can have overlapping physical properties, and substitute materials can have densities close to gold. Density is therefore supporting physical evidence, not a definitive purity assay.
Applications
Where Gold Density & Hydrostatic Testing Is Used
Bullion Screening
Add non-destructive physical information for suitable solid bars or bullion items.
Natural Nuggets
Examine suitable solid nuggets while recognising that shape, cavities and attached material affect interpretation.
Complementary Review
Combine density with surface elemental, internal structural or analytical testing where appropriate.
Suitable material
Materials and Sample Forms
- Suitable solid bullion
- Gold bars with an appropriate physical form
- Natural gold nuggets suitable for the procedure
- Other solid precious-metal items
Before testing
Sample Requirements
- The item must be a physically suitable solid specimen that can be weighed and, for hydrostatic testing, immersed without damage or trapped-air error.
- Irregular shape, surface contamination, attached material, cavities or porosity may affect volume measurement and interpretation.
- A parcel of nuggets should not be treated as uniform merely because one specimen is tested; each result describes the item or sample actually examined.
- Bilex confirms the procedure, measurement conditions and reporting terminology for the specific item.
Process
From Testing Question to Report
Identify the Item
Record the specimen and the physical-verification question.
Review Suitability
Check whether form, surfaces and condition support reliable mass and volume measurement.
Measure Mass
Obtain the item's mass under the confirmed measurement conditions.
Determine Volume
Use the agreed dimensional or hydrostatic approach to determine volume.
Calculate & Interpret
Calculate density and report it as supporting physical evidence with relevant limitations.
What it contributes
Strengths
- Normally non-destructive for a suitable solid item
- Provides direct mass-to-volume physical information
- Can help identify physical inconsistencies requiring review
- Can complement XRF, ultrasound or representative analytical testing
Scope
Limitations to Understand
- Cannot determine exact gold fineness by itself
- Different materials and alloys can have overlapping densities
- Some substitute metals have density close to gold
- Geometry, cavities, porosity and surface condition affect measurement
- Does not establish ownership, origin or wider transaction legitimacy
Method selection
How This Method Relates to Other Tests
Density, XRF and Ultrasound
Density provides information about an item's overall physical mass-to-volume relationship. XRF provides elemental information from selected surface regions. Ultrasound provides information about internal continuity.
These examinations are complementary and should not be presented as identical tests or as automatic substitutes for representative analytical determination.
Density and Fire Assay
Density testing normally preserves a suitable item and offers supporting physical evidence. Fire Assay consumes a representative analytical portion to determine gold under the applicable procedure.
When exact gold content or fineness is required, a density result alone is not a sufficient analytical conclusion.
Questions
Frequently Asked Questions
What is gold density testing?
It compares measured mass and measured volume to calculate an item's density and provide supporting physical information.
Is hydrostatic testing destructive?
It is normally non-destructive for a suitable solid item, although the item's condition and compatibility with immersion must be reviewed first.
Can density prove that a bar is pure gold?
No. Different compositions can have overlapping densities, and density alone cannot establish exact fineness.
Can density testing be used on natural nuggets?
It may be used on suitable solid specimens, but irregular shape, cavities and attached material can affect interpretation. One nugget does not represent an entire parcel.
Why combine density testing with another method?
Density answers a physical-consistency question. XRF, ultrasound and representative analytical methods provide different evidence about surface composition, internal structure or gold content.
Discuss the sample
Book Density Testing
Tell us the material, available sample quantity and the information the result needs to establish.
The final method and sample requirements are confirmed after the material and testing objective have been reviewed.