Enargite
Current inventory:  0 gems
 

  
Enargite is named from the Greek word enarges meaning visible, obvious or distinct, in allusion to its cleavage.

Discovery in 1850;   IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

Cu₃AsS₄

Copper Arsenic Sulfide

Molecular Weight:

393.82 gm

Composition:

Copper

48.41 %

Cu

Arsenic

19.02 %

As

Sulfur

32.57 %

S

100.00 %

Classification

Mineral Classification:

Sulfides

Strunz 8th Ed. ID:

2/C.14-10

Nickel-Strunz 10th Ed. ID:

2.KA.05

2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
K : Sulfarsenates, Sulfantimonates
A : Sulfarsenates with (As,Sb)S₄ tetrahedra

Related to:

Dimorph of Luzonite.

Varieties:

Argentian Enargite, Stannoenargite

Synonyms:

Clarite (of Sandberger), Garbyite, Guayacanite

Crystal Data

Crystallography:

Orthorhombic - Pyramidal

Crystal Habit:

Tabular on {001}; also prismatic by elongation of [001]; crystals up to 15 cm. Prism zone typically deeply striated k [001].

Twinning:

Twin plane {320} common, rarely as interpenetrating pseudohexagonal trillings.

Physical Properties

Cleavage:

Perfect on {110}, Distinct on {100} and {010}, Indistinct on {001} 

Fracture:

Irregular/Uneven

Tenacity:

Brittle

Moh's Hardness:

3.0

Density:

4.45 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Health Warning:

Contains Arsenic - always wash hands after handling. Avoid inhaling dust when handling or breaking. Never lick or ingest.

Optical Properties

Color:

Grayish Black to iron-Black; in polished section, Gray to pale Pink-Brown; deep Red internal reflections may be observed.

Transparency:

Opaque

Luster:

Metallic to Dull

Refractive Index:

R1–R2: (400) 24.8–26.2, (420) 26.6–26.0, (440) 26.5–25.6, (460) 26.5–25.9, (480) 26.2–25.8, (500) 25.6–25.6, (520) 24.9–25.3, (540) 24.4–25.2, (560) 24.0–25.2, (580) 23.8–25.4, (600) 23.8–25.9, (620) 24.1–26.5, (640) 24.6–26.9, (660) 25.2–26.9, (680) 25.6–26.8, (700) 25.7–26.7

Birefringence:

None; Opaque

Dispersion:

None

Pleochroism:

Weak

Anisotrophism:

Strong; dark violet red or olice green tones. Color in reflected light: grey to light pink brown. Internal reflections: deep red.

Occurances

Geological Setting:

In hydrothermal vein deposits formed at medium temperatures. Also as a late-stage mineral in low-temperature deposits.

Common Associations:

Pyrite, Sphalerite, Galena, Bornite, Tetrahedrite–Tennantite, Chalcocite, Covellite, Barite, Quartz

Common Impurities:

Sb, Fe, Pb, Zn, Ag, Ge

Type Locality:

San Francisco vein, Morococha District, Yauli Province, Junín Department, Peru

Year Discovered:

1850

View mineral photos:

Enargite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Enargite is a somewhat rare copper arsenic sulfide mineral that is dimorphous with Luzonite. This means the two minerals that have the same chemical formula (Cu3AsS4) but different crystal structures. Luzonite is Tetragonal and Enargite is Orthorhombic. Enargite does not often form well shaped crystals. However, there are several localities that produce some fine Enargite clusters. It is typically found as dark grey to black massive material. The rare crystals are usually thick tabular, but may also be prismatic. Twinning is common for Enargite and can form a nice star shaped cyclic twin called a trilling. Enargite has a metallic to dull luster and fairly soft with a Moh's hardness of only 3.0.

Distribution: A widespread mineral, may be an important ore of copper, but not commonly well-crystallized. Only a few localities can be mentioned. In Peru, from Morococha [TL] and Cerro de Pasco, with exceptional crystals from the Mina Luz Angelica, Quiruvilca. In Argentina, in the Sierra de Famatina, La Rioja Province. In the Philippine Islands, at Mancayan, Luzon. From the Chinkuashi mine, Keelung, Taiwan. At Kaize-mura, Nagano Prefecture, and in the Teine mine, Hokkaido, Japan. In the USA, in splendent crystals from Butte, Silver Bow County, Montana; in Utah, in the Tintic District, Juab County; in Colorado, in fine specimens from a number of mines in the Red Mountain district, San Juan County In Austria, at Matzenköpfl, Brixlegg, Tirol. From Bor, Serbia. In Italy, on Sardinia, at Alghero and Calabona. At Tsumeb, Namibia.
 

  
Enargite gems for sale:

We have not photographed our Enargite gems yet. Please check back soon.