Identification guide · Minerals
How to Identify Chalcocite
Chalcocite is dark gray to black with a metallic to dull luster, and it commonly tarnishes to blue, green, or iridescent surface colors. Streak is grayish-black, hardness is only 2.5 to 3, and unlike most sulfides it is sectile, meaning a knife can shave a thin sliver from it rather than gouge or crumble it. It is easily confused with bornite or covellite, but its sectility and lack of bornite's strong purple iridescence help separate the three.
Chalcocite identification checklist
| Color | Blackish lead-gray, Black | Look at a clean, dry surface in daylight. Color zoning, banding or spots are as diagnostic as the hue. |
|---|---|---|
| Luster | Metallic | Turn it under a lamp: a true metallic shine reflects like polished metal and stays opaque at thin edges. |
| Transparency | Opaque | Hold a thin edge up to a bright light and note whether light passes through. |
| Mohs hardness | 2.5–3 | A copper coin (Mohs 3.5) scratches it, but a fingernail does not. |
| Streak | Dark gray to black | Drag a corner across unglazed porcelain (the back of a bathroom tile) and check the powder color. |
| Cleavage | Poor, indistinct prismatic | |
| Fracture | Conchoidal | Broken surfaces show smooth, curved, shell-like scoops. |
| Specific gravity | 5.5–5.8 | Very heavy, metallic heft (specific gravity about 5.65). |
| Crystal system | Monoclinic |
Chalcocite look-alikes and how to tell them apart
Chalcocite is harder (Mohs 2.5–3) than Graphite (Mohs 1–2), so Chalcocite will scratch Graphite and not the other way round. A fingernail (Mohs 2.5) scratches it easily. Chalcocite vs Graphite →
Both sit near Mohs 2.5–3, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Chalcocite vs Bismuth →
Both sit near Mohs 2.5–3, so a scratch test alone will not separate them. Lean on luster, streak and heft instead. Chalcocite vs Copper →
Chalcocite is harder (Mohs 2.5–3) than Covellite (Mohs 1.5–2), so Chalcocite will scratch Covellite and not the other way round. A fingernail (Mohs 2.5) scratches it easily.
Chalcocite identification FAQ
How can you tell if a rock is Chalcocite?
Check the color (blackish lead-gray and black), the metallic luster, a Mohs hardness of 2.5–3 and a dark gray to black streak. Photographing it with the StoneSnap app gives a match in seconds.
What is the hardness of Chalcocite?
Chalcocite has a Mohs hardness of 2.5–3. A copper coin (Mohs 3.5) scratches it, but a fingernail does not.
What is the difference between Chalcocite and Graphite?
Chalcocite (Mohs 2.5–3, metallic luster) and Graphite (Mohs 1–2, metallic to dull/earthy luster) look alike, but hardness, streak and heft usually separate them. See the full Chalcocite vs Graphite comparison for a side-by-side table.
Is Chalcocite worth anything?
Entry-level Chalcocite specimens sell for around $2, typical collector pieces about $20, and premium examples $150 or more depending on size, quality and locality.
What color is Chalcocite?
Chalcocite is most often blackish lead-gray and black. Color varies with impurities and locality, so confirm with hardness and luster rather than color alone.
