Smooth surfaced, non-faceted cuts of gemstones, in any shape.

Cabochons Index

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Rainbow Calsilica (Cal Silica) - Mohs 3-4


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Realgar

Arsenic Sulfide. A major ore of arsenic that was once used for pigments because of its orange to red color. Unfortunately it degrades over time and old paintings that used it to produce reds now show yellows and oranges instead.

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Rhodochrosite - Mohs 4


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Rhodonite - Mohs 5.5-6.5


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Rhodonite-Rhodochrosite



Refers to a stone composed of both rhodonite and rhodochrosite. The interplay of the darker raspberry colored rhodonite and the pink and white of the rhodochrosite can be quite striking - especially when accented with black.

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Ruby-Fuchsite (Ruby in Fuchsite) - Mohs 2-3


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Ruby-Zoisite (Ruby in Zoisite) (Anyolite) - Mohs 6.5


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Rutilated Quartz - Mohs 7


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Rutile

Titanium oxide (a titanium ore) that is golden yellow to rusty yellow in thin crystals, becoming reddish brown to black as the crystals get thicker.

Microscopic inclusions of rutile in quartz, tourmaline, ruby, sapphire and other gemstones produces effects such as cat’s eye (chatoyancy) and stars (asterism).

Larger inclusions of rutile needles in clear quartz is called Rutilated Quartz.

Sagenite

Depending on who is using the term, they could be referring to Sagenitic Agate or Rutilated Quartz. While rutilated quartz may be a type of sagenite, it has a very defined type of inclusion - rutile. Sagenitic agate, on the other hand, seems to mean there can be various kinds of inclusions, as long as they are needle-like. (Agate is a type of cryptocrystalline quartz.)

Agate having needle-like mineral growths. These hair like filaments are often arranged in fans or sunbursts. The inclusions come in a wide array of colors. Inclusions occur where iron oxide, manganese oxide, or other oxides are present when the agate is formed. The oxide minerals grow in the agate when it is in a liquid or gelatinous state. The inclusions grow and are supported by this liquid medium. Sagenite seems to be named based on the geographic location it came from.

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Serpentine (Serpentinite, Serpentine Rock) - Mohs 5


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Shattuckite - Mohs - 3.5


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Sodalite - Mohs 5.5-6


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Sonoran Sunrise (Sonoran Sunset, Sonora Sunrise, Sonoran Sunrise)

See cuprite.

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Stalactite, Stalagmite

Mineral formations found on the ceilings and floors of caves. Stalactites are icicle-shaped. They form as minerals precipitate from groundwater seeping through the roof of the cave. As the water falls to the floor of the cave, minerals also precipitate and accumulate there. The mineral deposits on the floor grow upward and are called stalagmites. As they grow, stalactites and stalagmites can meet and create giant columns.

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Stibnite (Misspelling: Stebnite)

A steel-gray to silver ore of antimony with a metallic luster. Crystal formations of stibnite can be prized specimens.

Antimony is a metal (or semi-metal, since it is not as shiny and malleable as other metals). One of its leading uses is in the manufacture of flame retardants. It is also used as a pigmant (antimony oxide is brilliant yellow) and as a hardening alloy for lead.

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Sugilite - Mohs 6-6.5


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