Agate

Semi-precious stone, the Agate is said to improve natural vitality and energy and to increase the self-confidence of the person using it. It is believed to be of special benefit to athletes and to those taking any kind of examination or test - or anyone else who has to call upon instant bursts of energy whether mental or physical. Balances the emotions and calms the body, mind and feelings. General healing, reduces fever, hardens tender gums, gives courage and banishes fear, also assists the wearer to express thoughts into spoken words. Helps to develop powers of eloquence. Stone of health and good fortune.

Also, in many traditions agate is believed to cure the stings of scorpions and the bites of snakes, soothe the mind, prevent contagion, still thunder and lightning, promote eloquence, secure the favour of the powerful, and bring victory over enemies. Persian magi are also known to have prized agate rings in their work and beliefs.

Most agates occur as nodules in volcanic rocks or ancient lavas where they represent cavities originally produced by the disengagement of volatiles in the molten mass which were then filled, wholly or partially, by siliceous matter deposited in regular layers upon the walls. Such agates, when cut transversely, exhibit a succession of parallel lines, often of extreme tenuity, giving a banded appearance to the section. Such stones are known as banded agate, riband agate and striped agate.

In the formation of an ordinary agate, it is probable that waters containing silica in solution -- derived, perhaps, from the decomposition of some of the silicates in the lava itself -- percolated through the rock and deposited a siliceous coating on the interior of the vapour-vesicles. Variations in the character of the solution or in the conditions of deposit may cause corresponding variation in the successive layers, so that bands of chalcedony often alternate with layers of crystalline quartz.

A Mexican agate, showing only a single eye, has received the name of "cyclops agate." Included matter of a green, golden, red, black or other colour or combinations embedded in the chalcedony and disposed in filaments and other forms suggestive of vegetable growth, gives rise to dendritic or moss agate (named varieties include Maury Mountain, Richardson Ranch, Sheep Creek and others). Dendritic agates have beautiful fern like patterns on them formed due to the presence of manganese and iron ions. 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). 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.

Turritella agate is formed from fossil Turritella shells silicified in a chalcedony base. Turritella are spiral marine gastropods having elongated, spiral shells composed of many whorls. Similarly, coral, petrified wood and other organic remains or porous rocks can also become agatized. Agatized coral is often referred to as Petoskey agate or stone.

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. Often agate coexists with layers or masses of opal, jasper or crystalline quartz due to ambient variations during the formation process.

Other forms of agate include carnelian agate (usually exhibiting reddish hues), Botswana agate, Ellensburg blue agate, blue lace agate, plume agate (such as Carey, Graveyard Point, Sage, St. Johns, Teeter Ranch and others), tube agate (with visible flow channels), fortification agate (which exhibit little or no layered structure), fire agate (which seems to glow internally like an opal) and Mexican crazy-lace agate (which exhibits an often brightly coloured, complex banded pattern).