Final answer:
The untrue statement about hematite is that it contains iron and sulfur; it actually contains iron oxide and is known for its metallic appearance, red-brown streak, and use as an iron ore.
Step-by-step explanation:
The statement that is not true about the mineral hematite is: b) Hematite has a composition that contains iron and sulfur. Hematite is indeed a mineral that can appear metallic or earthy, which means choice a) is a correct solution. Hematite is also well-known for having a red-brown streak, and it is indeed an ore of iron, rich in oxidized iron, which makes choices c) and d) accurate statements.
Metals like iron usually do not occur naturally in their pure metallic form on Earth; instead, they are found as ores, often oxides, and in the case of hematite, it is specifically iron oxide without sulfur content. Hematite's streak is one of its identifying features, leaving a red-brown powder when scratched on a streak plate, distinguishing it from other minerals. Furthermore, its use as an ore of iron makes it an economically important mineral.