Chalcedony, also spelled Calcedony, is a very fine-grained (crypto-crystalline) variety of the silica mineral quartz. It has a waxy luster and appears in a great variety of colors -- usually blue-white, buff, light tan, gray, yellow or brown. Chalcedony is a catch all term that includes many well known varieties of cryptocrystalline quartz gemstones. They are found in all 50 States, in many colors and color combinations, and in sedimentary, igneous, and metamorphic rocks. Chalcedony includes carnelian, sard, plasma, prase, bloodstone, onyx, sardonyx, chrysoprase, thundereggs, agate, flint, chert, jasper, petrified wood, and petrified dinosaur bone just to name a few of the better known varieties. Because of its abundance, durability, and beauty, chalcedony was, except for sticks, animal skins, bones, plain rocks, and possibly obsidian, the earliest raw material used by humankind. The earliest recorded use of chalcedony was for projectile points, knives, tools, and containers such as cups and bowls. Early man made weapons and tools from many varieties of chalcedony including agate, agatized coral, flint, jasper, and petrified wood. A form of chert, it forms rounded crusts, rinds or stalactites (mineral deposits suspended from the roofs of caverns) in volcanic and sedimentary. It has a compact fibrous structure and fine splintery fracture. Other physical properties are those of quartz variously colored quartz with In the petrified forests of the Desert Southwest, many of the original tree tissues have been replaced by chalcedony in the formation of petrified wood. What remains is a mineral replica of the original tree in various fantastic colors. The brilliant reds and greens are caused primarily by traces of iron oxides. Some of the best displays of petrified wood can be seen in eastern Arizona's Petrified Forest National Park Chalcedony is a cryptocrystalline form of silica, composed of very fine intergrowths of the minerals quartz and moganite. These are both silica minerals, but they differ in that quartz has a trigonal crystal structure, whilst moganite is monoclinic. Chalcedony has a waxy lustre, and may be semitransparent or translucent. Its color is usually white to gray, grayish-blue or a shade of brown ranging from pale to nearly black. Other shades have been given specific names: A clear red chalcedony is known as carnelian or sard. A green variety colored by nickel oxide is called chrysoprase. Prase is a dull green. Onyx has flat black and white bands. Plasma is a bright to emerald- 1. Blue Chalcedony 14. Red Jasper 2. Chrysoprase 15. Willow Creek Jasper 3. Blue Chalcedony 16. Biggs Jasper 4. Blue Chalcedony 17. Onyx 5. Lavender Chalcedony 18. Sardonyx 6. Blue Chalcedony 19. Bloodstone 7. Chrysoprase 20. Chrysocolla 8. Carnelian 21. Tiger's Eye 9. Moss Agate 22. Chrysocolla 10. Plume Agate 23. Petrified Palm Wood 11. Blue Lace Agate 24. Petrified Dinosaur Bone 12. Fire Agate 25. Petrified Dinosaur Bone 13. Picture Jasper

green chalcedony that is sometimes found with small yellow spots of jasper. Heliotrope is similar to plasma, but with red spots of jasper, hence its alternative name of bloodstone. It is said that chalcedony was used as a sacred stone by the Native Americas, promoting stability within the ceremonial activities of the tribe. Chalcedony is said to augment emotional balance, vitality, stamina, endurance, kindness, charity and friendliness. It supposedly alleviates hostilities, irritability and melancholy. Chalcedony cameo of Titus head, 2nd Century ADPeople living along the Central Asian trade routes used various forms of chalcedony, including carnelian, to carve intaglios, ring bezels (the upper faceted portion of a gem projecting from the ring setting), and beads that show strong Graeco-Roman influence. Fine examples of first century objects made from chalcedony, possibly Kushan, were found in recent years at Tillya-tepe in north-western Afghanistan. Hot wax would not stick to it so it was often used to make seal impressions.

Chalcedony occurs in many varieties and colors. If chalcedony is conspicuously color-banded, it may be called agate and with other minerals it has various other names including: Agate: This common semiprecious variety of chalcedony is conspicuously color-banded with other minerals in successive layers. It occurs in bands of varying color and transparency in cavities of eruptive rocks or ancient lava. Agates come in many varieties themselves, including the following: Moss Agate: Also called Mocha Stone, this grayish to milky-white chalcedony contains dark-colored, dendritic branching forms that resemble ferns, moss, or other vegetation. These formations are caused by the inclusion of mainly manganese and iron oxides of inorganic origin. Most moss agates are found as fragments weathered from volcanic rocks and long used for ornamental purposes. Onyx: This striped, semiprecious variety of agate has black and white alternating bands. Onyx is used in carved cameos and intaglios because its layers can be cut to show a color contrast between the design and the background. Onyx is one of the 12 stones mentioned in the Bible as adorning the breastplate of the high priests. Bloodstone: Also called Heliotrope, this dark-green variety of chalcedony has nodules of bright-red jasper distributed throughout. Bloodstone was greatly prized in the Middle Ages and was used in sculptures representing flagellation and martyrdom. Carnelian: Translucent red chalcedony is called Carnelian, which owes its red to color to hematite (iron oxide). It is a close relative of Sard, which is brown in color. The Greeks and Romans used carnelian in rings and signets. Chrysoprase: This brittle, translucent form of chalcedony owes its bright, apple-green color to the inclusion of nickel silicates, but heating or prolonged exposure to sunlight causes the color to fade. Plasma: This semi-translucent, microgranular variety of chalcedony occurs in various shades of green, caused by amphibole or chlorite inclusions. Plasma often has nodules of gray quartz or Bloodstone throughout its mass. It has long been used for carvings and mosaics. The term chalcedony is derived from the name of the ancient Greek town Chalkedon in Asia Minor, in modern English usually spelled Chalcedon, today the Kadıköy district of Istanbul.  Carnelian Neon Blue Chalcedony Rough Blue Agate Chalcedony Colors Green Agate Blue Chalcedony Nodule

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