GEOLOGY

Detailed explanation-1: -Silicates-including quartz, mica, olivine, and precious minerals such as emeralds-are the most common class of minerals, as well as the major components of most rocks.

Detailed explanation-2: -Ironically, two of the hardest and best-known gem materials are not silicates: diamond, which is a native element, and corundum (varieties ruby and sapphire), which is an oxide. However, most of the rest of the best-known gemstone types are indeed silicates.

Detailed explanation-3: -The vast majority of the minerals that make up the rocks of Earth’s crust are silicate minerals. These include minerals such as quartz, feldspar, mica, amphibole, pyroxene, olivine, and a great variety of clay minerals.

Detailed explanation-4: -Roughly 90 percent of Earth’s crust is made up of silicate minerals. (The rest is mostly made up of oxide minerals-more on those next week!) These silicates, all of which contain silicon and oxygen atoms, are the basis of rock-forming minerals such as quartz, feldspars, micas, olivines, pyroxenes, and amphiboles.

Detailed explanation-5: -Gem silica is a bluish green to greenish blue variety of chalcedony that receives its vivid color from the presence of copper. It is often known as “chrysocolla chalcedony” or “gem silica chrysocolla."