• Chemistry: AgAuTe4, Silver Gold Telluride.
  • Class: Sulfides
  • Subclass: Tellurides
  • Uses: A very minor ore of silver and gold and as mineral specimens.
  • Specimens

Sylvanite is one of the few minerals that is an ore of gold, besides native gold itself. It is one of the most common gold bearing minerals. The element gold is typically either found as native gold (in its elemental state), as an alloy with other metals such as silver and copper and as trace amounts in a few minerals. To be an actual significant part of a non-alloyed mineral is really quite uncommon for gold and this makes sylvanite a unique mineral indeed.

For some reason gold has an affinity for the element tellurium, which is sometimes found naturally as native tellurium. Tellurium is a semi-metallic element which means that it has some properties of metals but not all or as strongly. This helps provide an explanation for gold's attraction to tellurium. Other gold tellurides include calaverite, (Gold Telluride); kostovite, (Copper Gold Telluride); krennerite, (Silver Gold Telluride); nagyagite, (Gold Lead Antimony Iron Telluride Sulfide) and petzite (Silver Gold Telluride). Calaverite is closely related to the more common sylvanite and differs in silver content and slightly in hardness, cleavage, color and density. At times the two minerals are only distinguishable with chemical tests.

Crystals of sylvanite are unique and of interest to collectors. Typically found as prisms that can be twinned causing sharp bends, reticulated individuals and skeletal or arborescent formations. These clusters remind many collectors of writing.


  • Color is a steel gray to silver gray to almost white.
  • Luster is a bright metallic.
  • Transparency: Crystals are opaque.
  • Crystal System: Monoclinic; 2/m
  • Crystal Habits include prismatic to more rarely tabular crystals that are often twinned into sharp bends, reticulated individuals and skeletal or arborescent formations. These are sometimes described as looking like writing. Also found as granular and columnar masses.
  • Cleavage is perfect in one direction.
  • Fracture is uneven.
  • Hardness is 1.5 - 2
  • Specific Gravity is approximately 8.2 (very heavy even for metallic minerals).
  • Streak is a steel gray to black.
  • Other Characteristics: Dark tarnish can often form after prolonged exposure to light.
  • Associated Minerals include gold, quartz, fluorite, rhodochrosite, pyrite, acanthite, nagyagite, calaverite, krennerite and other rare telluride minerals.
  • Notable Occurrences include Cripple Creek, Colorado and Calaveras County, California, USA; Nagyag, Romania; Bigstone Bay and Kirkland lake Gold District, Ontario and Rouyn District, Quebec, Canada; Kalgoorlie, Australia and Vahatala, Fiji.
  • Best Field Indicators are crystal habit, density, softness, color, luster, association with other tellurides and gold and cleavage.
SYLVANITE specimens:
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SYLVANITE specimen syl-1
$ 26.00
Dims: 0.4 x 0.2 x 0.2" (1.1 x 0.6 x 0.6 cm)
Wt: 7 g w/ base
Wahsburn Mine, Boulder County, Colorado, U.S.A.
This tiny thumbnail piece consists of a piece of host rock (likely quartz or quartzite) that contains a few small veins of semicrystalline Sylvanite. These veins are too small to effectively study even with a loupe, but show the standard silvery-white color and metallic luster of the mineral. The piece is attached to a flat acrylic base via a small post, and the base fits inside the included thumbnail box.
no photo
syl-1 ($ 26.00)
Wahsburn Mine, Boulder County, Colorado, U.S.A.
SYLVANITE specimen syl-2
$ 102.00
Dims: 0.8 x 0.5 x 0.3" (2.0 x 1.2 x 0.8 cm)
Wt: 2 g
Rex Mine, Boulder County, Colorado, U.S.A.
A crystalline Sylvanite formation extends from the quartz base of this thumbnail specimen. The formation is in excellent condition, showing no damage, and has dimensions of 0.3 x 0.2 x 0.1" (9 x 4 x 3 mm). Though the Sylvanite does not show any definite monoclinic form, it is certainly crystalline and has the classic silvery-white color and metallic luster of its specie. The base from which it extends contains a vein of either Sylvanite or possibly empressite that extends completely through it.
no photo
syl-2 ($102.00)
Rex Mine, Boulder County, Colorado, U.S.A.


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