Covellite
Covellite, CuS, is the indigo copper sulphide: hexagonal, hardness 1.5 to 2, density 4.6 to 4.76, one perfect cleavage. It is 66.47% copper; Cu2S is 79.86%.
Covellite is copper monosulphide, CuS, an IMA species (G, 1832): hexagonal, hardness 1.5 to 2, density 4.6 to 4.76, with one perfect {0001} cleavage and thin leaves that flex. It is indigo-blue, often iridescent, with a lead-gray streak. At 66.47% copper it carries one copper per sulphur, half the ratio of chalcocite, Cu2S.
In short
- The Cu–S ladder. Three independent scans of the September 2026 IMA-CNMNC Master List find exactly 11 rows written in copper and sulphur alone. By copper-to-sulphur ratio they run chalcocite and wuyanzhiite (Cu2S, 2.00), djurleite (1.94), digenite and roxbyite (1.80), anilite (1.75), geerite (1.60), spionkopite (1.39), yarrowite (1.125), covellite (CuS, 1.00) and villamanínite (CuS2, 0.50). Worked on standard atomic weights, covellite is 66.47% copper; chalcocite 79.86%.
- Soft by Mohs, not by Vickers. The Handbook of Mineralogy sheets give covellite a Mohs hardness of 1.5 to 2, a full step under chalcocite, digenite and djurleite at 2.5 to 3. At the same 100 g load, covellite’s Vickers figure is 128 to 138, above all three (84 to 87, 86 to 106 and 65 to 85). A scratch test and an indentation test put covellite at opposite ends of the four; the sheets give no reason, and this page offers none.
- Colour, as printed. The sheet’s colour field reads indigo-blue or darker, commonly highly iridescent, brass-yellow to deep red, with a lead-gray, shining streak. Its occurrence field adds that covellite is common as an iridescent tarnish on other sulfides, so an iridescent film on a copper sulphide may itself be covellite.
- Weight in water. At 4.6 to 4.76 a 20.00 g piece reads 15.65 to 15.80 g in water. That sits between chalcopyrite (15.12 to 15.35 g) and bornite (16.05 to 16.06 g), 0.30 g and 0.25 g from each, and 0.57 g under chalcocite’s lowest reading of 16.36 g.
- Where. The Distribution field gives Vesuvius, Campania [TL] and large crystals from the Calabona mine, Alghero, Sardinia; Bor, Serbia; Leogang, Austria; fine crystals in the primary ore at Butte, Montana; Kennicott, Alaska; and the Bou-Skour mine, Morocco, among others.
| Name | Formula (IMA) | IMA status | Cu:S | Copper by mass | Hardness (sheet) | Density (sheet) |
|---|---|---|---|---|---|---|
| Chalcocite | Cu2S | G, 1751 | 2.00 | 79.86% | 2.5 to 3 | 5.5 to 5.8 |
| Wuyanzhiite | Cu2S | A, 2017-081, China | 2.00 | 79.86% | No Handbook sheet (404) | No Handbook sheet |
| Djurleite | Cu31S16 | A, 1967 s.p., Mexico | 1.94 | 79.34% | 2.5 to 3 | n.d.; calc. 5.749 |
| Digenite | Cu1.8S; Handbook Cu9S5 | A, 1962 s.p., Germany | 1.80 | 78.11% | 2.5 to 3 | 5.546 |
| Roxbyite | Cu9S5 | A, 1986-010, Australia | 1.80 | 78.11% | n.d. (VHN 83) | n.d.; calc. 5.49 |
| Anilite | Cu7S4 | A, 1968-030, Japan | 1.75 | 77.62% | About 3 | n.d.; calc. 5.68 |
| Geerite | Cu8S5 | A, 1978-024, USA | 1.60 | 76.03% | Under 3.5 | n.d.; calc. 5.61 |
| Spionkopite | Cu39S28 | A, 1978-023, Canada | 1.39 | 73.41% | n.d. | n.d.; calc. 5.13 |
| Yarrowite | Cu9S8 | A, 1978-022, Canada | 1.125 | 69.04% | n.d. | n.d.; calc. 4.89 |
| Covellite | CuS | G, 1832, Italy | 1.00 | 66.47% | 1.5 to 2 | 4.6 to 4.76 |
| Villamanínite | CuS2; Handbook (Cu,Ni,Co,Fe)S2 | Rd, 1989 s.p., Spain | 0.50 | 49.78% | 4.5 | 4.4 to 4.5 |
What is covellite? The indigo copper sulphide
Covellite is copper sulphide with one copper atom to each sulphur, CuS. The Handbook of Mineralogy covellite sheet gives it hexagonal, point group 6/m 2/m 2/m, space group P63/mmc, forming hexagonal plates as large as 10 cm, flattened on {0001}, which may show hexagonal striae, and rosettes of nearly parallel plates; it is commonly massive and foliated. Cleavage is perfect on {0001}, the plates are flexible in thin leaves, hardness is 1.5 to 2 and measured density 4.6 to 4.76.
What the IMA list records. The September 2026 list gives covellite, CuS, status G (grandfathered, a mineral described before the IMA existed), 1832, with Italy as the country of first description and a first reference in the Traité Élémentaire de Minéralogie, 2nd edition (Paris, 1832). The sheet marks Vesuvius, Campania as the type locality and holds type material at the Mineral Museum, University of Naples, number 12338. The name honours Niccolò Covelli (1790–1829), who discovered the Vesuvian material.
Its chemistry, worked. On standard atomic weights CuS is 66.47% copper and 33.53% sulphur; the sheet prints 66.48 for the ideal. Its Butte, Montana analysis has Cu 66.06 and S 33.87, its Bor, Serbia analysis Cu 65.49 and S 33.45: atomic Cu:S ratios of 0.984 and 0.988, within two percent of one to one.
Where does covellite sit among the copper sulphides? The Cu–S ladder
Covellite is the most sulphur-rich of the 11 IMA copper sulphides except villamanínite. Method: the September 2026 list was converted with pdftotext -layout. A row parser split each line into name, formula and status; an independent scan took the second field of every line split on runs of two or more spaces; a third scan tested every whitespace token on every line. Each kept formulas made only of Cu and S with numeric subscripts. All three found the same 11, and chalcocite, djurleite, digenite and covellite were all found, as a positive control.
The ladder, worked. Dividing copper by sulphur in each IMA formula gives 2.00 for chalcocite and wuyanzhiite (both written Cu2S), 1.94 for djurleite, 1.80 for digenite and roxbyite, 1.75 anilite, 1.60 geerite, 1.39 spionkopite, 1.125 yarrowite, 1.00 covellite and 0.50 villamanínite, CuS2. Copper by mass falls from 79.86% to 49.78% down the same list. The Handbook prints villamanínite as (Cu,Ni,Co,Fe)S2 and digenite as Cu9S5; the table shows both.
What the ladder does and does not settle. It places covellite chemically; it does not identify a specimen. Of the eleven, only chalcocite, digenite, covellite and villamanínite have a measured density on their sheets, and the copper-rich end is where hand identification fails, which is the subject of the chalcocite page. Covellite is easier: its sheet gives the indigo colour, the single perfect cleavage and the 1.5 to 2 hardness, and none of the nine other Handbook sheets on the ladder uses the word indigo; spionkopite and yarrowite, the two nearest covellite, are described as blue. Magnetic separation figures for covellite and its neighbours are on is malachite magnetic and are not repeated here.
Why is covellite iridescent, and how hard is it?
The sheet records covellite as commonly highly iridescent, and as an iridescent tarnish on other sulphides. Its colour field reads indigo-blue or darker, commonly highly iridescent, brass-yellow to deep red; pleochroism is marked, deep blue to pale blue. Its occurrence field says it is most commonly of secondary origin in the zone of oxidation of copper sulphide deposits, rarely primary hydrothermal, widespread in most copper deposits and common as an iridescent tarnish on other sulfides. The sheet gives no cause for the iridescence and this page offers none. How an iridescent surface on chalcopyrite or bornite should be read is on is chalcopyrite the same as peacock ore; its density line is not repeated here.
A documented mismatch between two hardness scales. Four of the copper sulphide sheets give both a Mohs range and a Vickers figure at a 100 g load. By Mohs, covellite at 1.5 to 2 is the softest of the four; chalcocite, digenite and djurleite are all 2.5 to 3. By Vickers indentation at a 100 g load the order turns over: covellite 128 to 138, digenite 86 to 106, chalcocite 84 to 87, djurleite 65 to 85. A scratch reading alone would call covellite the weakest of the four; an indentation reading would not. The technique and its limits are on how to test mineral hardness properly.
Streak and cleavage. Covellite leaves a lead-gray, shining streak, as do chalcocite and galena; the indigo colour and the flexible {0001} leaves are what separate it in the hand. The methods are on how to use a streak plate and cleavage or fracture.
Where covellite is found: Calabona, Butte and Vesuvius
The Distribution field says covellite has numerous localities, with only a few producing rich material: Vesuvius, Campania [TL], and large crystals from the Calabona mine, Alghero, Sardinia, Italy; Bor, Serbia; Leogang, Salzburg, Austria; Dillenburg, Hesse, and Sangerhausen, Saxony, Germany; Kedabek, Caucasus Mountains, Russia; the Bou-Skour mine, Bou Azzer district, Morocco; in the USA, Butte, Silver Bow Co., Montana, as fine crystals in the primary ore, Kennicott, Alaska, Summitville, Colorado, and the La Sal district, Utah, and a widespread but minor constituent of the ores in most porphyry copper mines in Arizona; and the Sierra de Famatina, La Rioja, Argentina.
What it grows with. The sheet’s association line is chalcopyrite, chalcocite, djurleite, bornite, enargite, pyrite and other sulfides. The copper minerals it is found with have their own pages: chalcocite, bornite, chalcopyrite and native copper; whether native copper counts as a mineral is answered on is copper a mineral.
Weighing it. A 20.00 g piece of covellite reads 15.65 to 15.80 g in water, worked as 20 − 20/D. The method is on how to measure specific gravity at home. The rest of the reference section is at the species index. We hold no catalogue and nothing here is offered for sale; the wanted list is the only commercial route.