Petalite: Petalite is a lithium aluminum silicate that is an important ore of lithium. This mineral forms, ra... (read full)

Peridot: Peridot is the greener type of gem-quality specimen of Forsterite-Olivine, which is an important, ro... (read full)

Pearl: Pearl is one of four main ornamental materials that are classified as "organic" gems, the ... (read full)

Padparadscha: Padparadschah is the name given to the orange-yellow sapphire, a gem variety of Corundum. It is also... (read full)

Orthoclase: Orthoclase mineral is a silicate of potassium and aluminum, belonging to the Feldspar group. It has ... (read full)

Opal: Opal is hydrated silicon dioxide. It has the same chemical composition as quartz but contains about ... (read full)

Onyx: Onyx is a translucent to semitransparent variety of Agate, which in turn is a variety of Chalcedony ... (read full)

Oligoclase: Oligoclase is a mineral of the plagioclase feldspar series, other members of which are Labradorite a... (read full)

Obsidian: Obsidian is an extrusive igneous rock, a volcanic glass formed by rapid cooling. Its essential com... (read full)

Nephrite: Nephrite is a silicate of calcium, magnesium, and iron, containing fluorine and hydroxyl. It is an a... (read full)