Raw carnelian appears quartz-like in texture.
Chalcedony shares its chemical composition with crystalline quartz. The distinction separating these two stones lies in their formation. While quartz appears independently, chalcedony forms in crevices or cavities of other rocks. Variations of color and pattern exist due to metallic particles and other inclusions in the soft, porous stones. These qualities make chalcedony popular with crafters and gemologists.
Bloodstone
Although green in color, bloodstone derives its name from red speckles caused by deposits of hematite. The stones can appear glossy or waxy and usually have at least some level of translucency. Used by jewelers for carved items such as cameos and men's signet rings, bloodstone forms in North and South America, China, India, Australia and parts of Europe.
Carnelian
Carnelian is translucent, waxy and cloudy in appearance. Although it gets its name from the Latin word carneas, meaning fleshy, its color can range from oranges and tans to deep reds. Ancient Romans ascribed feminine leanings to the lighter shades and masculine to the darker. Carnelian appears throughout the world in locations as varied as the United States, Japan and Madagascar.
Agate
Agates form in openings in volcanic rock, and can vary widely in color and translucency. Their shared characteristic is their banded appearance. The bands occur in concentric patterns, mimicking seashells, and theories suggest either pockets of gas or drops of liquid create them. Agate appears in North and South America, Australia, Europe and Africa.
Chrysoprase
Chrysoprase deposits often occur in nickel ore, and inclusions of this metal inside the stones create their greenish hues. Collected from Polish mines as early as the 14th century, chrysoprase once appeared inside buildings as an ornamental stone. Modern uses include jewelry and decorative objects crafted from stones found in Russia, South Africa, Brazil and other parts of the world.
Sard
Sard is often confused with Carnelian due to their similar brown and red hues, but sard's color tends to be more muted and closer to brown than red. Recognizable as the medium for Victorian cameo jewelry, this stone gets its color from deposits of limonite, a type of iron oxide. It appears in India, China, Sri Lanka and the United States.
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