Stachybotrys chartarum (often referred to as ‘Stachybotrys atra’ or ‘black mold’) is typically greenish-black in color, and found on surfaces in areas where high levels of moisture is present - black mold pictures can be seen below. Common causes of high moisture levels include: excessive humidity, water leakage/damage, condensation, and floods.
In addition to moisture, black mold requires a nutrient (food source) for significant growth to take place. A familiar nutrient that black mold thrives on is cellulose, a widespread organic compound found just about anywhere. Examples in a home or building include: drywall, ceiling tile, various paper-based products, wood, upholstery, carpeting, and different fabrics.
Because many species of mold can be black in color, it is not recommended or necessary to “test” mold; rather, any and all mold found in a home should be treated as potentially dangerous and discarded, cleaned, or handled by a professional. Here are some of the most common areas in which black mold can be found, including actual pictures of black mold on each:

Black mold growing on the baseboard of an interior wall.

Black mold on ceiling, caused by HVAC problems.

Black mold on wooden wall studs and exterior sheeting.

Black mold on ceiling tiles after a minor roof leak.

Black mold forming beneath a leaky garbage disposal.

Black mold growing on the ceiling of an attic.

Black mold growing under carpeting, near a shower.

Black mold in a small, dark corner near a door stop.

Black mold behind a toilet, underneath the drywall.

Black mold on restaurant walls, behind the wallpaper.

Black mold severely contaminating the walls of a home.

Black mold found behind the tile of a shower.