646 Tiger striped agate obelisk is handy size for decor as well as transporting from place retailer to place fits in pocket or purse for protection.

646 Tiger striped agate obelisk is handy size for decor as well as transporting from place to place fits in pocket or purse for protection.

Agate - The stone was given its name by Theophrastus, a Greek philosopher and naturalist, who discovered the stone along the shore line of the river Achates (Ancient Greek: Ἀχάτης) in Sicily,[2] sometime between the 4th and 3rd centuries BC.[3] Colorful agates and other chalcedonies were obtained over 3,000 years ago from the Achates River, now called Dirillo.
Agate is one of the most common materials used in the art of hardstone carving, and has been recovered at a number of ancient sites, indicating its widespread use in the ancient world; for example, archaeological recovery at the Knossos site on Crete illustrates its role in Bronze Age Minoan culture.[4]
Most agates occur as nodules in volcanic rocks or ancient lavas, in former cavities produced by volatiles in the original molten mass, which were then filled, wholly or partially, by siliceous matter deposited in regular layers upon the walls. Agate has also been known to fill veins or cracks in volcanic or altered rock underlain by granitic intrusive masses. 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 retailer 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 gel in the interior of the vesicles. Variations in the character of the solution or in the conditions of deposition may cause a corresponding variation in the successive layers, so that bands of chalcedony often alternate with layers of crystalline quartz. Several vapour-vesicles may unite while the rock is still viscous, and thus form a large cavity which may become the home of an agate of exceptional size; thus a Brazilian geode lined with amethyst and weighing 35 tons was exhibited at the Düsseldorf Exhibition of 1902. Perhaps the most comprehensive review of agate chemistry is a recent text by Moxon cited below.
Many agates are hollow, since deposition has not proceeded far enough to fill the cavity, and in such cases the last deposit commonly consists of drusy quartz, sometimes amethystine, having the apices of the crystals directed towards the free space so as to form a crystal-lined cavity or geode.
When the matrix in which the agates are embedded disintegrates, they are set free. The agates are extremely resistant to weathering and remain as nodules in the soil, or are deposited as gravel in streams and along shorelines.
Agates can also be found in sedimentary rocks. They need a cavity to form, so they are typically seen in limestone, dolomite, and shale which may have shells, tree branches, or roots in them that later decay away. With the void created, silica-rich fluids can enter the cavity and precipitate chalcedony in curved bands forming agates. Other quartz classes like amethyst or opal may then form the inner-most band inside the geode.[5]