Native silver
Native silver is hardness 2.5 to 3, density 10.1 to 11.1 and ductile. Only three species in this site's reference set are malleable: gold, silver and copper.
Native silver is elemental silver, Ag, cubic, with a hardness of 2.5 to 3, a hackly fracture and no cleavage. Measured density is 10.1 to 11.1 and 10.5 when pure. It is one of only three species in this site's 158-sheet reference set whose tenacity is recorded as malleable and ductile, alongside gold and copper, and that property separates the three native metals from every sulphide that imitates them.
In short
- Ductility is the test, not hardness or colour. Of 122 sheets in this site's reference set that record a tenacity, exactly three say malleable and ductile: gold, silver and native copper. Everything else is brittle, sectile or flexible. A silver wire bends and flattens under a pin; acanthite crumbles and galena cleaves.
- Density and microhardness run in opposite directions across the three native metals. Gold 19.3, silver 10.1 to 11.1, copper 8.95 on measured density — but VHN 30 to 34, 60 to 65 and 77 to 99 on microhardness. The heaviest of the three is the softest, and the lightest is the hardest.
- Most wire silver in a collection is black, and much of it is not silver on the surface. The Handbook records silver as tarnishing grey to black, and acanthite, Ag2S, is the usual coating. Acanthite is hardness 2 to 2.5 and density 7.20 to 7.22, so a tarnished wire is a two-mineral object.
- Crystallised silver is uncommon; wire, arborescent and reticulated growths are the norm. The Handbook gives cubic, octahedral and dodecahedral crystals only to 2 cm, against wire growths that are the classic Kongsberg and Freiberg specimens.
- Analysis of Kongsberg material gives 98.450% Ag with 1.130% Hg. Native silver is an alloy in practice, not a pure metal, and mercury, antimony, gold, copper and iron are the usual company.
| Species | Formula | Hardness | Density | How it differs in the hand |
|---|---|---|---|---|
| Silver | Ag | 2.5 to 3 | 10.1 to 11.1 | Ductile and malleable; hackly fracture; no cleavage |
| Gold | Au | 2.5 to 3 | 19.3 | Very malleable and ductile, but nearly twice the density and it does not tarnish |
| Copper | Cu | 2.5 to 3 | 8.95 | Highly malleable and ductile; red where fresh, green where oxidised |
| Acanthite | Ag2S | 2.0 to 2.5 | 7.20 to 7.22 | Sectile rather than ductile, iron-black with a black streak; it is the usual coating on tarnished silver |
| Chlorargyrite | AgCl | 2.5 | 5.556 | Plastic, resinous to adamantine lustre, and it darkens on exposure to light |
| Stephanite | Ag5SbS4 | 2 to 2.5 | 6.26 | Brittle with an iron-black streak; a sulphide, not a metal |
| Galena | PbS | 2.5 to 2.75 | 7.58 | Perfect cubic cleavage, which silver does not have at all |
The one test that works, and why hardness is not it
Silver, gold and native copper all sit at hardness 2.5 to 3. So does chlorargyrite at 2.5, and galena and acanthite are within half a point. A scratch test cannot separate any of them. The scratch test and its limits are set out on how to test mineral hardness properly.
Tenacity can. Counted across the Handbook of Mineralogy sheets for the 158 species in this site's reference set, 122 record a tenacity and exactly three of those say malleable and ductile: gold (very malleable and ductile), silver (ductile, malleable) and copper (highly malleable and ductile). Nothing else in the set behaves that way.
The practical version: press a fine wire of the specimen with a pin, out of sight on the back. Silver deforms and stays deformed. Acanthite, which is sectile, shaves and crumbles. Galena parts along a cleavage plane. Stephanite and the silver sulphosalts are simply brittle. One test, no reagents, and it distinguishes a native metal from every sulphide that imitates one.
The caution is the obvious one: this is a destructive test on a soft species, so it belongs on a hidden wire end, not on the face of the specimen. A specimen that cannot afford a pin mark cannot afford this test.
Density and microhardness rank the three native metals in opposite orders
This is a small result and it is genuinely useful. Taking the Handbook's own figures for the three malleable species in the reference set:
Measured density: gold 19.3, silver 10.1 to 11.1, copper 8.95. Vickers microhardness: gold VHN 30 to 34 at a 10 g load, silver VHN 60 to 65 and copper VHN 77 to 99, both at 100 g.
The order inverts completely. The densest of the three is the softest by indentation, and the lightest is the hardest. Mohs cannot see this — all three read 2.5 to 3 — because Mohs is an ordinal scale and a 2.5-to-3 bracket is wide enough to hide a factor of two in indentation hardness. The same point in a different species pair is made on whether marcasite is the same as pyrite.
Density alone will still separate gold from silver without any equipment beyond a balance and a glass of water, because 19.3 against about 10.5 is not a subtle difference. The method is on how to measure specific gravity at home. Note one trap the arithmetic creates: silver's measured range of 10.1 to 11.1 brackets uraninite's 10.63, so density alone does not distinguish those two — though nothing else about them is remotely similar.
Where native silver actually comes from, and what it is found with
The Handbook records silver as a primary hydrothermal mineral that also forms by secondary processes, especially in the oxidised portions of a deposit, associated with acanthite, chlorargyrite, embolite, the silver sulphosalts, gold and copper.
The classic crystallised and wire localities named on the sheet are Kongsberg in Norway, where the Handbook says development is exceptional; Freiberg, Marienberg and St Andreasberg in Germany; Příbram and Jáchymov in the Czech Republic; Monte Narba in Sardinia; the Keweenaw Peninsula in Michigan, where it grows with native copper; Cobalt and Silver Islet in Ontario; and many Mexican districts.
British native silver is real but minor. It is a component of several of the Welsh and Scottish lead-silver orefields and turns up in the Cornish and Devon lodes, but it is not what this country is collected for. The British strengths are elsewhere: the copper arsenates of Cornwall, the fluorite of Weardale and the campylite of the Caldbeck Fells.
The rest of this reference section is indexed at the species index. We hold no catalogue and nothing here is offered for sale; the wanted list is the only commercial route, and good Kongsberg and Cobalt wire silver is on it.