determined the specific gravity hydro-statically to be 3.36. The visible-light spectroscopy of the same Chinese peridot samples showed light bands between 493.0 and 481.0 nm, the strongest absorption at 492.0 nm. Inclusions are common in peridot crystals but their presence depend on the location it is found at and the geological conditions that led to the crystallization of the peridot. Primary negative crystals — rounded gas bubbles — form in-situ with peridot and are common in Hawaiian peridots. Secondary negative crystals form in peridot fractures. Lily pad cleavages, seen often in San Carlos peridots, are a type of secondary negative crystal and are viewed easily under reflected light as circular discs surrounding a negative crystal. Silky and rod-like inclusions are common in Pakistani peridots. The most common mineral inclusion in peridot is the chromium-rich mineral chromite. Magnesium-rich minerals also can exist in the form of pyrope and magnesiochromite. These two types of mineral inclusions typically surrounded lily-pad cleavages. Biotite flakes appear flat, brown, translucent, and tabular. The largest cut peridot olivine is a specimen in the Smithsonian Museum in Washington, D.C. Cultural history Peridot has been prized since the earliest civilizations for its claimed protective powers to drive away fears and nightmares, according to superstitions. It is believed by some superstitious people to carry the gift of "inner radiance", sharpening the mind and opening it to new levels of awareness and growth, helping one to recognize and realize one’s destiny and spiritual purpose. There is no scientific evidence for such claims. Peridot is sometimes mistaken for emeralds and other green gems. Notable gemologist George Frederick Kunz discussed the confusion between emeralds and peridot in many church treasures, notably the "Three Magi" treasure in the Dom of Cologne, Germany. Peridot olivine is the birthstone for the month of August. Gallery References External links Ganoksin Mineralminers USGS peridot data Emporia Edu Florida State University – Peridot Gemstones Silicate minerals