Silver
Native silver is a beautiful and interesting mineral, that has quite a following among
mineral collectors ... even if it is rarely crystallised! One of the most desired habits of
Silver is the wire habit, elongate curled wires of metallic Silver, covered by a thin skin
of black silver sulfide. Particularly Kongsberg in Norway is famous for such specimens,
but they also occur in deposits in Germany, Mexico and elsewhere.
Specimens of wire Silver, supposedly from Grube Himmelsfürst in Freiberg
(Germany), caused considerable controversy in 2000-2001 [see f.ex. letters to the editor,
in particular issues 2/2001 and 3/2001 of the German journal Mineralien Welt]. The
basic point is, that it is possible to grow Silver wires synthetically rapidly and without
much equipment (see f.ex. Jensen, 1939), and individuals claimed some/most of a
considerable number of specimens labeled Grube Himmelsfürst that suddenly
came on the market were indeed synthetic. Others were equally adamant that the
specimens were completely natural. Whatever the truth is, any wire Silver without
associate minerals (and indeed people are prone remove Calcite and silver sulfides with
acid to produce more aesthetically pleasing specimens!) is suddenly under scrutiny, and
even verifiable antique or remarkably large specimens are not out of the spotlight. The
French mineralogist René Just Hauy described the technique around 1800, and
some people managed to grow wires to 7-9 cm in experiments following the controversy
and rediscovery of the technique.
Most of the larger deposits of native Silver are probably formed by hydrothermal
processes, and are normally assigned to one of three types, depending on the associate
minerals. The Uraninite-Nickel-Cobalt type is known from a.o. Jáchymov
(Joachimsthal) (Bhmen, Czech Republic) and Johanngeorgenstadt (Sachsen, Germany).
The sulfide-zeolite type, occurring in a gangue of Calcite, Fluorite, Quartz, and Barite
may be represented by the famous deposit in Kongsberg (Norway - and no, this is not
one mine but a collection of about 300 different pits, adits, etc.!). Finally, the nickel-
cobalt type with arsenides is represented by Cobalt (Ontario, Canada). Note, that these
deposits exploit or exploited native Silver as an ore, but today by far the largest volume
of silver is extracted from Galena, lead ore. Most Galena carries traces of silver, up to
as much as 1-2% by weight, but this is invariably bound as silver sulfides. Native Silver
is also known from the copper mines in the Keweenaw Peninsula (Michigan, USA),
where particularly 'half breeds' - nuggets of intergrown native Silver and native Copper
- are highly cherished, though some of the copper mines have produced very collectable
specimens of Silver crystals. These are deposited in a basalt at far higher temperatures,
than the hydrothermal deposits mentioned above.
Silver very often contains even appreciable amounts of either mercury or gold, and a
number of varieties and independent minerals have been named. The classic 'Elektrum'
is Silver with very high proportion of gold.
Associate minerals
Our records indicate that Silver from a range of deposits occurs on specimens that also
carry one or more of the following minerals: Achantite, Ägirine, Annabergite,
Argentopyrite, Arsenic, Arsenolamprite, Barite, Bayldonite, Beudantite, Biotite,
Bornite, Brochantite, Calcite, Carminite, Cerussite, Chalcocite, Chalcopyrite,
Chlorargyrite, Connellite, Copper, Cuprite, Cuprostibite, Dolomite, Dyscrasite,
Embolite, Epidote, Erythrite, Fluorite, Galena, Gersdorffite, Goethite, Graphite,
Harmotome, Lautite, Limonite, Lllingite, Magnetite, Malachite, Mixite, Pearceite,
Proustite, Pyrite, Quartz, Safflorite, Scolecite, Serpierite, Sodalite, Sphalerite,
Stromeyerite, and Xanthoconite.
Specimen Handling
Silver is for all practical purposes stable in a normal household environment, except it is
prone to tarnish. It is not harmed by light, changes in temperature in the normal
comfort range, or known to decompose, apart from the tarnish. Silver specimens can be
brittle and should be handled with care like any other mineral specimen. Silver is not
appreciably soluble in water.
It is possible to prevent or retard tarnish of silver specimens, but it invariably involves
some kind of surface coating. The black tarnish is silver sulfide, forming by reaction of
the native silver with sulfur dioxide in the atmosphere. In particular bright, strongly
cleaned specimens are prone to tarnish rapidly, but it depends on the amount of sulfur
dioxide in the atmosphere.
If you wish to protect your Silver specimens, we recommend you ask your local
museum, and an historic museum is likely as good as or better than a natural history -
they often have a number of objects made from silver or other metals, and will know
which products are available. If you choose to apply varnish to a specimen, you must
ensure it can be dissolved again years from now and will not discolour, and that the
luster is near that of Silver. Note, a surprising number of modern varnishes polymerize
and can not be dissolved again after they have 'dried'. Some collectors of antique silver
ware, who have the same problem, but who do not wish to varnish their collection, place
a piece of camphor on the top shelf of their cabinet. The camphor evaporates slowly,
and deposits a thin film, protecting the specimens. At least it leaves an intense scent of
camphor in the cabinet, that is not at all unbecoming for antique silver ware!
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This page is authored by Claus Hedegaard.
Mineraler