Red Jasper is an opaque, microcrystalline variety of chalcedony, which is a form of quartz. This material is primarily silicon dioxide, but its characteristic deep red coloring comes from iron oxide impurities, specifically hematite. Historically favored for seals and ornamentation, Red Jasper is now popular in jewelry and decorative arts due to its rich color and durability.
Observing Basic Visual Traits
The color of genuine Red Jasper ranges from pale orange-red to deep, earthy brick-red or reddish-brown. While the color can be uniform, it often displays mottled patterns, stripes, or veins of darker browns or blacks, characteristic of its formation. This rich color results from iron content evenly distributed throughout the silica structure.
A defining visual characteristic is its total opacity; no light should pass through the stone, even when examined along the edges. If the material is translucent, it is not Red Jasper, but likely a similar quartz material such as Carnelian. When polished, Red Jasper exhibits a waxy, dull, or subvitreous luster, reflecting light softly rather than with a high glassy sheen.
Testing Physical Properties
The most practical test for authentic Red Jasper is its hardness, rated between 6.5 and 7 on the Mohs scale. This means the stone is hard and resistant to scratching from common household items. A simple scratch test can be performed on common window glass, which has a Mohs hardness of 5.5.
Genuine Red Jasper should easily scratch the glass surface, leaving a permanent groove. Conversely, a steel nail (hardness 5.5 to 6.5) should not easily scratch the surface of the Red Jasper. When broken, the material displays a conchoidal fracture—a smooth, curved, shell-like break typical of quartz and glass. The stone’s density, ranging from 2.5 to 2.9 grams per cubic centimeter, contributes to a noticeably heavy feel compared to lighter plastic imitations.
Distinguishing Red Jasper from Imitations
Red Jasper is sometimes confused with or imitated by other materials. The most common lookalike is Carnelian, which is a translucent red-orange chalcedony that allows light to pass through its structure. Red Aventurine is another similar stone, but it features a distinctive shimmering effect called aventurescence, caused by tiny, reflective flecks of mica inclusions. Red Jasper completely lacks this sparkle, presenting a solid, matte surface.
When inspecting dyed stones or plastic imitations, look closely at the color distribution, especially in any natural fissures or cracks. Artificially dyed materials often show a concentration of color in these crevices, or the color saturation may appear unnaturally uniform. Plastic or glass imitations can be identified through a simple temperature test, as genuine stone feels cool against the skin and takes longer to warm up than a synthetic material.