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.
The choice between marble and granite depends on the aesthetic effects you want to achieve and how much use or abuse the stone will be subjected to. Although both are natural stones and quarried from the earth, granite and marble (and marble's relatives-limestone, onyx and travertine) are very different from each other.orn from molten magma, granite is a much more durable and functional stone than marble. Granite's crystalline structure is far more resistant to abrasions, staining and discoloration than most marbles.