peridot is gem-quality olivine and a silicate mineral. its green color is affiliate on the iron contents within the structure of the gem. the molecular structure of peridot consist of isomorphic olivine, silicate, magnesium and iron in an orthorhombic crystal system.
sapphire is a precious gemstone, a type of the mineral corundum, include of aluminum oxide with trace amounts of elements such as iron, titanium, chromium, vanadium, or magnesium.
opal is a hydrated amorphous form of silica. because of its amorphous character, it is classed as a mineraloid, unlike crystalline forms of silica, which are classify as minerals.
