What does black mold look like?

Last updated: 2026-07-06 · Reviewed by the DisasterStatus editorial team

Black mold usually looks like dark green-black, greenish-gray, or charcoal patches — slimy or slightly shiny when it's actively growing on a wet surface, drying to a powdery, soot-like film — and often comes with a musty, earthy smell. "Black mold" is the name homeowners give to this dark growth on a damp wall, ceiling, or baseboard, most often the species Stachybotrys chartarum, which the CDC describes as a greenish-black mold that grows on damp, cellulose-rich materials — though several ordinary molds look similar. You usually can't identify the exact species by eye, but you can learn to recognize what mold looks like versus a harmless stain, and that's enough to know whether you have a moisture problem worth acting on. Here's what to look for.

Color

Despite the name, "black" mold is rarely a pure, even black. Active growth is typically a dark green-black, greenish-gray, or charcoal color, sometimes with a faint olive or brownish tint at the edges (Stachybotrys chartarum is described as a greenish-black mold by the CDC). As a patch dries out it can look more flat black and sooty. Be careful with color alone, though: mildew and many household molds also show up as black or gray speckling, and not everything dark is mold at all (see "what gets mistaken for it" below).

Texture

Texture is one of the more telling clues. When Stachybotrys is actively growing on a wet surface it often looks slimy, wet, or slightly shiny, almost like a smear of dark paint or grease. As it dries it becomes powdery and soot-like, and can smudge or release dust if disturbed. Other molds look fuzzy, cottony, or velvety rather than slimy. Any of these textures — slimy, powdery, or fuzzy — points to mold rather than a stain.

Pattern and where it grows

Mold grows outward from a moisture source, so it tends to form circular, blotchy, or irregular spreading patches rather than the straight lines or uniform discoloration you'd get from water staining or dirt. Look for it where moisture collects:

• Bathroom walls, ceilings, grout, and around tubs and showers
• Under and behind sinks, dishwashers, and washing machines
• Basement and crawl-space corners, and the bottom edge of drywall
• Around windows with condensation, and on ceilings under a roof leak
• On wood framing, paper-faced drywall, ceiling tiles, and cardboard — Stachybotrys grows on materials with high cellulose content such as fiberboard, gypsum board, and paper (CDC)

Smell

Mold often announces itself before you see it. A persistent musty, earthy, "old basement" odor — strongest in one area, or worse after rain or when the HVAC runs — is a classic sign of active growth, sometimes hidden inside a wall or above a ceiling; the CDC notes that mold can smell musty and that if you see or smell it you should remove it. If you can smell mold but can't find it, treat the smell as real evidence and keep looking (or have it inspected).

What gets mistaken for black mold

Plenty of dark marks aren't mold. Before you panic, rule out the look-alikes:

• Dirt, soot, and grime — wipe a small area with a damp cloth. Dirt comes off cleanly and stays gone; mold smears, may smell musty, and grows back.
• Mildew — a surface mold that's usually gray/white and powdery, easier to clean, and stays on the surface rather than rooting into the material.
• Water stains — brown or yellowish rings with no texture and no smell; a sign of past moisture, not necessarily active mold (though they tell you to check for it).
• Efflorescence — white or grayish mineral salts that crystallize on concrete and brick basements. It's crusty and dissolves in water; mold doesn't.

The reliable tell: mold is tied to moisture and it comes back. If a dark patch is in a damp area, has a musty smell, smears or feels slimy/fuzzy, or returns after cleaning, treat it as mold.

Color can't confirm the species — only testing can

It's worth being clear: you cannot tell Stachybotrys from other dark molds by looking, and even a lab ID doesn't change the basic homeowner playbook — the CDC notes that the color of mold doesn't necessarily indicate how dangerous it is and that it isn't necessary to determine the type of mold, because all molds should be treated the same. What matters is that visible mold means you have excess moisture: the CDC advises that you clean up the mold and fix the moisture problem, and growth on porous materials needs to be removed properly so it doesn't spread or return. If you want the species identified — or you suspect hidden growth — that's what a mold inspection is for. For more on telling whether you have a mold problem at all, see signs of mold in your house, and for the health angle, is black mold dangerous?

When to call a pro

A small patch of surface mold on a hard, non-porous surface can often be cleaned by a homeowner — the EPA says that if the moldy area is less than about 10 square feet (a patch roughly 3 ft by 3 ft) you can in most cases handle the job yourself. Call a professional when the area is larger, when mold is on or behind porous materials like drywall or insulation, when it keeps coming back, when you smell mold but can't find it, or when it followed a flood or sewage backup. A remediation pro will contain the area, remove affected materials safely, and — most importantly — fix the moisture source so it doesn't return. Connect with a vetted local mold remediation pro to get matched.