A shared reference library for the whole MazalGold workspace: understand units and fineness, see what testing equipment actually does, check standard coin content, and read the technical melting guide.
Reference only: MazalGold does not test, authenticate or grade items, does not price collector value and gives no scores. For transaction paperwork and regulatory orientation, visit the separate Compliance desk.
How alloy families behave, why a scale difference is not the same as gold loss, and what to record before assigning a process-loss percentage. Includes a fume-hazard boundary and source-checked mass-balance workflow.
MazalGold’s precious-metal spot prices in U.S. dollars are quoted per troy ounce. The trade desk accepts weights in grams, troy ounces or pennyweights. Unit definitions below are exact; conversions are rounded.
Mass
Unit
Grams
Troy oz
Note
Troy ounce (ozt)
31.1034768
1
480 grains; 20 pennyweights
Pennyweight (dwt)
1.55517384
0.05
24 grains
Grain (gr)
0.06479891
1/480
The same grain in troy and avoirdupois
Gram (g)
1
0.0321507
Kilogram (kg)
1,000
32.1507466
Troy pound
373.2417216
12
Rarely used
Avoirdupois ounce (oz)
28.349523125
0.9114583
Kitchen and postal scales; 8.85% lighter than a troy ounce
Avoirdupois pound (lb)
453.59237
14.5833333
7,000 grains
Metric carat (ct)
0.2
—
Gemstone weight. On UK and some other jewelry, “ct” marks gold fineness instead (9ct, 18ct).
Regional units such as the tola, tael and baht are not listed. Confirm the gram weight the bar or its maker states.
Fineness
Karat is parts of gold in 24; millesimal fineness is parts per 1,000. The percentage and parts-per-1,000 columns below are nominal karat ratios. Nearby marks are not always numerically identical to those ratios. A stamped mark states a claimed fineness, not a test result. Fineness and hallmarking source.
Karat
Gold
Parts per 1,000
Marks encountered (not exact equivalents)
9K
37.50%
375.0
375, 9ct
10K
41.67%
416.7
10K, 417
14K
58.33%
583.3
14K, 583, 585
18K
75.00%
750.0
18K, 750
22K
91.67%
916.7
22K, 916, 917
24K
100%
1,000
24K, 999, 999.9
Marks such as GF, GP, RGP, HGE, “1/20 14K” or vermeil mean a layer of gold over another metal, not karat gold throughout.
Bars and many bullion coins are stamped with the purity they claim, such as 999.9; some coins state only their fine gold weight.
Read a numeric mark literally: 585 claims 58.5% gold, not the nominal 14/24 = 58.33%; 990 claims 99%, 999 claims 99.9%, and 999.9 claims 99.99%. These are different finenesses, not exact synonyms for pure gold.
The trade desk’s karat presets use the fractions above, with 24K set to 99.99%. A preset or stamp is not an assay of the item.
Density of pure metals
Typical tabulated elemental densities, rounded from the cited NIST table—not exact authentication standards. Density depends on material condition and temperature; an alloy is not the same material as its pure constituents.
Metal
g/cm³
Platinum
21.45
Gold
19.32
Tungsten
19.30
Rhodium
12.41
Palladium
12.02
Lead
11.35
Silver
10.50
Copper
8.96
Nickel
8.90
Iron
7.87
Tin
7.31
Zinc
7.13
By the figures above, tungsten is within about 0.1% of gold. Ordinary density screening cannot authenticate an item or reliably rule out tungsten on that difference.
Alloys are not pure metals. The density of karat gold, sterling or coin silver depends on the metals in the alloy, so there is no single correct figure for 14K or 18K.
Sources
NIST Office of Weights and MeasuresNIST Handbook 44 (2026), Appendix C — General Tables of Units of Measurement
Appendix C (PDF)https://www.nist.gov/document/2026-nist-handbook-44-appendix-cChecked October 3, 2026
NIST Physical Measurement LaboratoryX-Ray Mass Attenuation Coefficients — Table 1, material constants for elements (density)
Table 1 — element densitieshttps://physics.nist.gov/PhysRefData/XrayMassCoef/tab1.htmlChecked October 3, 2026
Birmingham Assay OfficeGold assay and hallmarking — millesimal fineness standards
Gold fineness and hallmarkinghttps://www.theassayoffice.co.uk/our-services/hallmarking/gold-assay-and-hallmarking/Checked October 3, 2026
Testing methods and equipment
These are different physical tests, not interchangeable authenticity detectors. A single screening result is not a complete authentication: the right method depends on the item, the question being asked and the operator’s skill. MazalGold does not test or authenticate items, does not accept photos for authentication and gives no authenticity score.
Magnet
What it is
A simple attraction check using a handheld magnet, not an electronic purity meter.
Equipment
A suitable handheld magnet and a way to bring it near the item without scratching the surface.
Reads
Noticeable magnetic attraction, such as from iron or many steels. Stainless steel’s response depends on its alloy and processing.
Can show
Magnetic material is present where a strong pull occurs. A steel clasp spring can respond even when the rest of a jewelry piece does not.
Limits
No attraction does not establish precious-metal content: many base metals and tungsten also lack a strong pull. A response from one component does not identify the bulk item or determine its fineness.
Effect on item
Non-destructive when handled without contact damage; do not drag the magnet across the finish.
A chemical comparison of a rubbed metal streak with streaks from test needles of known fineness.
Equipment
A touchstone, known-fineness test needles, fresh test acids appropriate to the metal, and the protective equipment and trained chemical handling the acid supplier specifies.
Reads
How the sample and comparison streaks react to the test acids.
Can show
An approximate gold-fineness range for the metal transferred to the stone.
Limits
The streak may represent only a surface layer, not metal under plating, gold-filled stock or an internal filling. Acid condition, reference needles, alloy composition and the tester’s judgment affect the comparison; it is not an exact bulk assay.
Effect on item
Abrasion removes a little metal. Filing through a surface layer leaves a mark, and misplaced acid can damage the item.
A hydrostatic weighing check: compare the item’s balance reading in air with its apparent reading while suspended in water.
Equipment
A balance with suitable resolution, a water vessel and a suspension or density kit that keeps the item submerged without touching the vessel. Account for the support, water temperature and attached air bubbles.
Reads
The usual approximate ratio is SG = mair ÷ (mair − msubmerged). Here msubmerged is the item’s apparent balance reading on the suspension—not a beaker-on-scale displacement reading. Specific gravity (SG) is dimensionless; estimated density = SG × water density at the measurement temperature.
Can show
An overall density inconsistent with the claimed metal or alloy, when the item and setup suit this method.
Limits
Ordinary screening cannot reliably distinguish gold from tungsten (19.32 vs 19.30 g/cm³), or identify fineness. Hollow or filled items, attached stones, tiny samples, trapped bubbles and measurement uncertainty can invalidate a simple comparison.
Effect on item
Requires immersion. Do not use on materials, settings or finishes that can be harmed by water; check suitability first.
An electronic spectrometer directs X-rays at the item and analyzes characteristic X-rays emitted by the material.
Equipment
An XRF instrument purpose-calibrated for precious metals, suitable reference standards and a trained operator following the instrument’s radiation-safety requirements.
Reads
Elemental composition in the near-surface region reached by the measurement. There is no single universal sampling depth: it depends on the material, elements and instrument conditions.
Can show
Estimated elemental concentrations in the measured region; suitable instruments and methods can also investigate some coatings.
Limits
A surface result does not establish the composition of the whole item or rule out an internal core. Coatings, contamination, shape, measurement position and calibration affect the result.
Effect on item
Generally non-destructive as measured; any surface preparation must be considered separately.
An electronic non-destructive-testing (NDT) thickness gauge or flaw detector sends high-frequency sound pulses into metal and receives returning echoes. It is not an ultrasonic jewelry-cleaning bath.
Equipment
A suitable instrument and contact transducer (the probe that sends and receives sound), manufacturer-approved couplant (a gel or liquid that excludes air between probe and metal), a calibration/reference sample, a caliper or other measured-thickness reference, and a trained operator.
Reads
Echo travel time and, with appropriate equipment, echo patterns. Calculated thickness depends on the sound velocity entered for the material; an incorrect velocity can produce a misleading thickness.
Can show
Unexpected echoes or a mismatch between acoustic and measured thickness can flag a discontinuity, void or possible different-material insert for investigation. Flat, parallel bar surfaces are favorable for simple through-thickness screening.
Limits
A simple thickness gauge is not automatically a full flaw detector. Probe choice, scan coverage, shape, surface condition, calibration and interpretation limit what can be found; complex jewelry or coin relief can frustrate a basic setup. It does not measure gold fineness, and there is no universal “pass” reading for every product.
Effect on item
Normally non-destructive, but confirm that the couplant and probe contact are compatible with the finish and follow the maker’s cleaning guidance.
A professional laboratory assay that separates and measures precious metal from a prepared sample. Cupellation followed by suitable separation and weighing is an established method for gold fineness.
Equipment
A properly equipped assay laboratory with sample-preparation facilities, a high-temperature furnace, cupellation equipment, an analytical balance and trained staff. This is not a home testing procedure.
Reads
The gold content of the analyzed sample under the laboratory’s stated method and uncertainty.
Can show
A quantitative gold-fineness result for a representative sample. The laboratory selects its method for the alloy and other elements present; fire-assay methods also exist for other precious metals.
Limits
A result does not describe unsampled portions unless the sampling plan makes it representative. Inhomogeneous material, sampling and interfering elements must be addressed by the laboratory.
Effect on item
Destructive: a sample is cut, drilled or taken from a representative melt and consumed in the analysis.
A matching screening result is one piece of evidence, not a universal authenticity certificate. Conflicting results call for a qualified laboratory or specialist and a method appropriate to the item.
Equipment descriptions explain what the tests involve; they are not operating instructions or laboratory procedures. Sources and their verification status follow.
Sources
NIST Physical Measurement LaboratoryX-Ray Mass Attenuation Coefficients — Table 1, material constants for elements (density)
Table 1 — element densitieshttps://physics.nist.gov/PhysRefData/XrayMassCoef/tab1.htmlChecked October 3, 2026
Gemological Institute of America · Gems & GemologyMethods for Determining Gold Content of Jewelry Metals (1992)
GIA technical paper (PDF)https://www.gia.edu/doc/Methods-for-Determining-Gold-Content-of-Jewelry-Metals.pdfChecked October 3, 2026
Gemological Institute of AmericaTouchstone testing of karat gold — equipment, comparison and precautions
GIA touchstone testing guidehttps://www.gia.edu/bench-tip-use-the-touchstone-method-for-testing-purity-karat-goldChecked October 3, 2026
Evident · instrument manufacturerUltrasonic testing of gold bars
Silver content from each coin’s legal weight and fineness. Metal content only: no collector values, grades or price guides.
Coin
Standard weight
Silver
Silver per coin
Dime, 1873–1964
2.50 g
90%
2.25 g · 0.07234 ozt
Quarter, 1873–1964
6.25 g
90%
5.625 g · 0.18085 ozt
Half dollar, 1873–1964
12.50 g
90%
11.25 g · 0.36170 ozt
Morgan or Peace dollar, 1878–1935
26.73 g
90%
24.06 g · 0.77344 ozt
Kennedy half dollar, 1965–1970
11.50 g
40%
4.60 g · 0.14789 ozt
Wartime nickel, 1942–1945, large P, D or S above Monticello
5.00 g
35%
1.75 g · 0.05626 ozt
Weights are the legal standard for unworn coins. Dimes, quarters and halves dated before 1873, and some dated 1873, were struck to other weights or finenesses; this table does not apply to them. Circulation dimes and quarters dated 1965 or later, and half dollars dated 1971 or later, are copper-nickel clad with no silver. Some later proof and collector coins are silver, such as 40% silver Eisenhower dollars and silver proof sets, and Morgan and Peace design dollars are again struck from 2021 on; use that coin’s own specification.
$1 face value of 90% dimes, quarters or halves
Basis
Silver
What it is
Unworn (1873–1964 standard)
0.72339 ozt per $1 face
Arithmetic from the standard: $1 face is 25.00 g of 90% silver, 22.50 g of silver, in any mix of dimes, quarters and halves.
Circulated (0.715 convention)
0.715 ozt per $1 face
A dealer convention that allows for average wear, about 1.2% below unworn. It is not a legal standard or a measurement, and MazalGold found no official source for it. A real lot can be heavier or lighter.
Weighed lot
net grams × 0.900 ÷ 31.1034768 = ozt
Silver in a lot of genuine 90% dimes, quarters and halves after removing clad, 40%, wartime nickels, dollars and foreign coins. The coins are one alloy throughout, so wear does not change the 90% ratio.
Morgan and Peace dollars stay off the junk-silver shortcut
Count them per coin at 0.77344 ozt each, never by face value at 0.715. A dollar is 412.5 grains of 90% silver: about 7% more silver per $1 face than unworn dimes, quarters and halves, so the 0.715 shortcut undercounts it by about 7.6%.
The table’s 26.73 g is a rounded display. The silver figure uses the unrounded standard: 412.5 grains × 0.900 ÷ 480 grains per troy ounce = 0.7734375 ozt, shown as 0.77344 ozt.
0.77344 ozt is the unworn standard; a worn dollar holds its own weight × 0.900.
Copies and private-mint rounds with these designs are common. The figures apply only to genuine coins.
Date, mint mark and condition can add collector value. MazalGold does not grade coins or price collector value and uses no price guides.
In Coin values: circulated 90% dimes and quarters, and circulated 90% halves, use 0.715 ozt per $1 face (their 25 g gross weight is the unworn weight); Morgan and Peace dollars are a separate item at 0.77344 ozt per coin; 40% Kennedy halves use a 0.295 ozt trade factor per $1 face (unworn 0.29579); wartime nickels are 0.05626 ozt per coin. Morgan and Peace dollars show “Melt is not a collectible valuation — review first”.
Sources
U.S. Bureau of the Mint · via FRASER, Federal Reserve Bank of St. LouisDomestic and Foreign Coins Manufactured by Mints of the United States, 1792–1965
FRASER catalog pagehttps://fraser.stlouisfed.org/title/domestic-foreign-coins-manufactured-mints-united-states-1792-1965-6280Checked October 3, 2026