Native silver

Native Silver
A cluster of bright silver, wire-like, and crystalline metallic mineral protruding from a dark, grayish-black matrix.
Native silver specimen exhibiting robust crystallization from the Imiter Mine, Ouarzazate Province, Morocco (miniature size 4.3 × 4.1 × 2.1 cm)
General
CategoryNative metal
FormulaAg
Strunz classification01.AA.05
Dana classification1.1.1.3
Crystal systemIsometric (Cubic)
Crystal classHexoctahedral (m3m)
H-M symbol: (4/m 3 2/m)
Space groupFm3m
Unit cella = 4.086 Å; Z = 4
Identification
ColorSilver-white on freshly exposed surfaces; readily tarnishes to yellow, brown, dark gray, or black upon exposure to atmospheric hydrogen sulfide (H2S)
Crystal habitCommonly massive, arborescent, dendritic, or as filiform (wire-like) twisted aggregates. Rarely as macroscopic cubes, dodecahedra, or octahedra.
TwinningVery common on ⟨111⟩, producing reticulated and complex dendritic arrays
CleavageNone
FractureHackly
TenacityHighly malleable and ductile; sectile
Mohs scale hardness2.5–3.0
LusterMetallic
StreakSilver-white (shining)
DiaphaneityOpaque
Specific gravity10.1–11.1 (pure is 10.5; varies with presence of gold or copper)
Melting point961.78 °C (1,763.20 °F)
Fusibility2
Diagnostic featuresHigh specific gravity, distinctive silver-white shining streak, extreme ductility, complete solubility in nitric acid
SolubilitySoluble in nitric acid and heated concentrated sulfuric acid
Other characteristicsExhibits the highest electrical (6.30 × 107 S/m) and thermal conductivity of any metal at room temperature.

Native silver is a naturally occurring native element mineral consisting of the chemical element silver (Ag) in its pure, uncombined metallic form. It crystallizes in the cubic crystal system (isometric) with lattice parameter a = 4.086 Å and space group Fm3m. Silver has an average continental crustal abundance of approximately 0.056 parts per million (ppm). While rarely found in its elemental state, it more commonly occurs in compound forms such as sulfide minerals or sulfosalt minerals. Native silver occurs with crystallographic habits including filiform (wire-like), arborescent, and dendritic structures in hydrothermal veins, and constitutes only a minor fraction of global production, which is primarily sourced as a by-product from base-metal ores.

This page is issued from Wikipedia. The text is available under Creative Commons Attribution-Share Alike 4.0 unless otherwise noted. Additional terms may apply for the media files.