Agates are extremely resistant to weathering and remain as nodules in the soil or are deposited as gravel in streams and shorelines.
Today any agate of this color from Greek/Sicily area of the Mediterranean is called Greek agate.
Shi'a Muslims often wear an agate ring on the right hand, the stone engraved with the name of Allah, Ali, or the names of the other eleven Imams.
Dendritic agates have beautiful fern like patterns on them formed due to the presence of manganese and iron ions.
Such stones are known as banded agate, riband agate, and striped agate.
Often agate coexists with layers or masses of opal, jasper or crystalline quartz due to ambient variations during the formation process.
The colorful agate and other chalcedonies were obtained over 3,000 years ago from the Achates River (now called the Drillo) in Sicily.
Agates are used to make ornamental objects such as pins and brooches, and items with practical uses such as paper knives, inkstands, and seals.
Turritella agate is formed from fossil Turritella shells silicified in a chalcedony base.
Agates have been used in history to make both ornamental objects and practical items, including brooches, paper knives, inkstands, and seals.
Many agates are hollow, because deposition has not proceeded far enough to fill the cavity.
Most agates occur as nodules in volcanic rocks or ancient lavas.
Some have thought that agate has powers that can be used for love, mental clarity, and good luck in card games.
Other types of included matter deposited during agate-building include sagenitic growths (radial mineral crystals) and chunks of entrapped detritus (such as sand, ash, or mud).
Agate is a type of quartz (silica), chiefly chalcedony, characterized by its fine grain and bright colors.
The first deposit on the wall of a cavity, forming the "skin" of the agate, is generally a dark greenish mineral substance, like celadonite, delessite, or "green earth."
Agbayani lists 238 species for which the common name bass, basslet, bassi, or ambasse specifically is applied.
Certain stones, when examined in thin sections by transmitted light, show a diffraction spectrum due to the extreme delicacy of the successive bands, whence they are termed rainbow agates.
A Mexican agate, showing only a single eye, has received the name of "cyclops agate."
The green silicate may be altered to a brown iron oxide (limonite), giving a rusty appearance to the outside of the agate-nodule.
Greek agate is a name given to pale white to tan-colored agate found in Sicily back to 400 B.C.E.
Occasionally agate fills a void left by decomposed vegetative material such as a tree limb or root and is called limb cast agate due to its appearance.
Another type of agate is Brazilian agate, which is found as sizable geodes of layered nodules.
Such agates, when cut transversely, exhibit a succession of parallel lines, giving a banded appearance to the section.