For iron sulfide, two elements (sulfur and iron) are heated together so that they form the compound iron sulfide. Although iron sulfide contains both sulfur and iron, it is not a mixture: it is a pure substance. Both the sulfur and the iron have 'given up' their individual properties to become a compound.
Gneiss. Gneiss is a hard rock that has a mineral composition similar to granite as it contains the feldspar, mica, and quartz. This is a rock that is formed from pre-existing igneous rocks such as granite that have been subject to conditions of high pressure and temperature.ranite is a hard igneous rock that is mostly made up of feldspar and quartz. Granite has a crystalline structure, and it can have a wide range of colors from grey to pink. The color of a granite rock is dependent upon the composition of minerals.
Gneiss (pronounced nice) is a type of metamorphic rock that forms when a sedimentary or igneous rock is exposed to extreme temperatures and pressure. When this happens, virtually no traces of the original rock remain. Gneiss rocks are characterized by their arrangement of minerals into long bands. Interesting Gneiss Facts: Gneiss is distinctive among other rocks that have bands because its minerals are not evenly distributed so the bands are various widths. Under appropriate conditions, gneiss can be recrystallized into granite. There is gneiss in Canada that date back 4 billion years.