Blue sillimanite cabochon in rose cut, in 16×5 mm round format and 16×11×4 mm teardrop format.
Item details
| Mineral |
Sillimanite (Al₂SiO₅ — polymorph of kyanite and andalusite) |
| Dimensions |
Round: 16×5 mm · Teardrop: 16×11×4 mm · ±0.5 mm due to artisanal cutting |
| Shape and back |
Round and teardrop, rose cut (faceted dome), flat back |
| Finish |
Lapidary polish with rose facets |
| Hardness |
6-7 Mohs — we recommend a closed bezel setting |
| Origin |
India |
| Treatment |
Color treated (artificial color enhancement). The blue-violet color is not natural to the mineral. |
| Item type |
Available in round and teardrop formats |
This particular piece
Sillimanite is an aluminum silicate (Al₂SiO₅) that shares its formula with kyanite and andalusite — they are polymorphs of each other, formed under different temperature and pressure conditions.
The rose cut adds between 12 and 24 flat facets to the dome, which increases the internal brilliance and visual presence of the piece at the expense of eliminating the characteristic smoothness of a conventional cabochon.
What mounting it works for
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Pendants with open-back settings or sterling silver 925 bezels — the rose cut works particularly well in open-back settings that allow light to enter through the back and enhance the brilliance of the facets. It also works in a closed bezel, with a more contained profile.
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Statement rings by artisan jewelers — the intense blue-violet color and facets give this cabochon a greater visual presence than many opaque gems. For unique designs where the rarity of the material is part of the piece's narrative.
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Wire wrap — the rose cut in wire wrap produces a multiple sparkle effect when the wire catches the light at different points on the facets. A feasible technique for jewelers experienced in wire wrap on faceted gems.
Sillimanite in gemology
Sillimanite belongs to the aluminum silicate group along with kyanite and andalusite, three minerals with the same chemical formula (Al₂SiO₅) but distinct crystal structures, each stable under different temperature and pressure ranges.
In crystal traditions, sillimanite is associated with mental clarity and decision-making. The blue color added by treatment does not alter its physical structure but expands its aesthetic possibilities for use. The symbolic properties attributed to minerals belong to cultural and historical traditions. They are shared for educational purposes, not as medical advice.
How to recognize genuine sillimanite
Untreated natural sillimanite is colorless, brown, or greenish — never indigo blue. Intense blue pieces of this mineral indicate color treatment: this information must always be declared.
Frequently asked questions
Is the blue color natural?
No. Natural sillimanite is colorless, brown, or greenish. The indigo to violet blue color of these pieces has been obtained through a color enhancement treatment applied before cutting. We explicitly declare this because it is relevant information for the buyer.
Is the color treatment permanent?
Color treatments on minerals are usually stable under normal use and storage conditions. Avoid prolonged exposure to intense sunlight or extreme heat, which can affect the stability of the treatment over time.
What is the actual hardness of the mineral?
Sillimanite has 6-7 Mohs depending on the measurement plane. It is sufficient for jewelry, although we recommend a closed bezel to protect the edges of the rose cut.
What is the difference between the round and teardrop formats?
The round (16×5 mm) has more frontal visual presence; the teardrop (16×11×4 mm) is more elongated and suitable for dangling earrings and neck pendants. Both have the same rose cut on the dome.
Are the measurements exact?
The indicated measurements are for reference with a tolerance of ±0.5 mm in any dimension due to being artisanally cut.
How is it cared for?
Clean with a soft, damp cloth. Avoid prolonged sun exposure and sudden temperature changes. More tips in jewelry care.
See also: complete cabochon collection.
