Luzonite
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Luzonite is named after the type locality, Mancayan, Luzon, Philippines.

Discovered in 1874; 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 and Sulfosalts

Strunz 8th Ed. ID:

2/C.06-10

Nickel-Strunz 10th Ed. ID:

2.KA.10

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:

Stannite Group. Luzonite-Famatinite Series. Dimorph of Enargite.

Members of Group:

Stannite Group: Briartite, Černýite, Famatinite, Ferrokësterite, Ge-stannoidite, Hocartite, Kësterite, Kësterite Subgroup, Keutschite, Kuramite, Luzonite, Permingeatite, Petrukite, Pirquitasite, Stannite, Velikite 

Varieties:

Stannoluzonite

Synonyms:

Stibioluzonite (of Stevanović)

Crystal Data

Crystallography:

Tetragonal - Scalenohedral

Crystal Habit:

Crystals rare, to 2 mm; commonly coarse-grained, fine-grained, massive, intimately intergrown with Enargite.

Twinning:

Common on {112}, also polysynthetic in polished section. 

Physical Properties

Cleavage:

Good on {101}, distinct on {100}

Fracture:

Irregular/Uneven, Conchoidal

Tenacity:

Brittle

Moh's Hardness:

3.5

Density:

4.38 - 4.60 (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:

Deep pinkish brown, similar to Bornite, although darker; in polished section, pale brownish pink

Transparency:

Opaque

Luster:

Metallic, dull

Refractive Index:

R1–R2: (400) 27.2–28.7, (420) 25.6–27.6, (440) 24.1–25.6, (460) 23.6–24.7, (480) 23.4–24.5, (500) 23.7–25.2, (520) 24.1–26.4, (540) 24.3–27.1, (560) 24.9–27.7, (580) 25.6–28.5, (600) 26.5–29.1, (620) 27.3–29.6, (640) 28.1–29.9, (660) 28.6–30.1, (680) 28.7–30.0, (700) 28.7–30.0

Birefringence:

0.000 (opaque)

Dispersion:

n/a

Pleochroism:

Weak

Anisotropism:

Strong, in greenish yellow and purplish

Occurances

Geological Setting:

In hydrothermal Cu–As–Sb-rich vein and disseminated deposits, formed at low to medium temperatures.

Common Associations:

Enargite, Tetrahedrite–Tennantite, Colusite, Stannoidite, Pyrite, Chalcopyrite, Covellite, Sphalerite, Bismuthinite, Silver sulfosalts, Silver, Gold, Marcasite, Alunite, Barite, Quartz.

Common Impurities:

Sb

Type Locality:

Lepanto Mine, Mancayan mineral district (Mankayan), Benguet Province, Cordillera Administrative Region, Luzon, Philippines

Year Discovered:

1874

View mineral photos:

Luzonite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Luzonite is a somewhat rare copper arsenic sulfide mineral that is dimorphous with Enargite. This means the two minerals that have the same chemical formula (Cu3AsS4) but different crystal structures. Luzonite is Tetragonal and Enargite is Orthorhombic. Luzonite is opaque with metallic luster, Moh's hardness of 3.5 and very dark pinkish brown color.

Locations for Luzonite: from the type locality [TL] at the Lepanto mine, Mankayan, Luzon, Philippines, as an ore mineral. In the Chinkuashi mine, Keelung, Taiwan. In Japan, at the Teine, Morino, and Date mines, Hokkaido; the Kasuga and Akeshi mines, Kagoshima Prefecture; and other localities. From the Sierra Famatina, La Rioja Province, Argentina. In the Julcani district, at Cerro de Pasco, and at Huaron, Peru. In the USA, in Nevada, at Goldfield, Esmeralda County, from the Golden Chariot mine, Jamestown district, Nye County, and in the Burrus vein, Pyramid district, Washoe County; from Butte, Silver Bow County, Montana; and at Summitville, Rio Grande County, Colorado. At the Chelopech deposit, Sofia, Bulgaria. From Calabona, Sardinia, Italy. At the Kadzaharan deposit, Armenia. From Pîrîul lui Avram, Romania. In the Lahóca Hill mine, Recsk, Mátra Mountains, Hungary. Numerous additional localities are now known.
 

  
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