UV-Reactive Septarian Polished Slab – Madagascar – 0.67 lbs

A striking two-sided polished Septarian Slab from Madagascar, featuring a dramatic network of golden calcite-filled fractures surrounded by deep brown mineral borders and contrasting gray limestone sections. Both broad faces have been polished, allowing the specimen’s naturally divided patterns and internal mineral structure to be appreciated from multiple viewing angles.

The slab displays the classic appearance that makes Madagascar septarian highly recognizable. Angular gray host-rock sections are separated by branching brown seams, while translucent honey-yellow calcite fills several larger fractures and cavities. Under direct lighting, the calcite reveals internal cleavage patterns and a warm luminous glow that contrasts beautifully with the matte-looking gray sections.

This specimen is also UV reactive. Fluorescence is concentrated within responsive mineral areas—most commonly the calcite—creating a second display appearance under ultraviolet illumination. The visible color and intensity may vary depending on the wavelength and strength of the UV light used.

Measuring approximately 5 × 0.5 × 5.5 inches and weighing 0.67 pounds, this substantial slab provides excellent cabinet presence without requiring a large display footprint. Its two polished faces, natural outer edges, bold fracture pattern, translucent calcite, and fluorescence make it an appealing geological display piece.

Specifications

Material: Septarian stone with calcite-filled fractures

Specimen Type: Two-sided polished slab

Locality: Madagascar

Weight: 0.67 lbs (approximately 304 grams)

Dimensions: Approximately 5 × 0.5 × 5.5 inches

Color: Gray, dark brown, golden yellow, cream, and honey tones

Primary Features: Contrasting septarian pattern with translucent calcite-filled veins and cavities

Finish: Both broad faces polished with natural outer edges

UV Response: Fluorescent mineral areas; appearance may vary by UV wavelength

Transparency: Opaque host material with translucent calcite sections

Condition: Natural stone slab with inherent fractures, mineral contacts, surface variations, and irregular edges

Display: Freestanding or stand-mounted collector display

Exact specimen shown

About Septarian Stone

Septarian stone is a lapidary and collector name applied to concretions or nodules containing distinctive networks of mineral-filled fractures. The name derives from the Latin word septum, meaning partition, referring to the naturally divided appearance created by these internal cracks.

Septarian formations developed as mineral-rich sediment hardened around a central mass. Shrinkage and other geological stresses produced fractures within the concretion, which were later filled by minerals carried through the surrounding sediment. Calcite commonly forms the golden-yellow crystalline areas, while brown mineral layers and gray carbonate-rich host material create the familiar contrasting pattern.

When a septarian nodule is cut and polished, its internal fracture system becomes visible as an intricate natural mosaic. No two slabs share the same arrangement, making each piece a unique record of sedimentary formation and later mineral deposition.

Calcite can fluoresce under ultraviolet light when trace elements or structural defects activate its response. Fluorescence can differ considerably under longwave and shortwave UV illumination, so photographs taken with one lamp may not perfectly represent its appearance under another.

Collector Notes

This specimen features:

• Natural septarian material from Madagascar
• Two broad polished display faces
• Dramatic gray and dark brown partitioned pattern
• Translucent honey-yellow calcite sections
• Visible calcite cleavage and internal crystalline detail
• UV-reactive mineral areas
• Different appearance under visible and ultraviolet light
• Natural irregular perimeter
• Substantial size with a slim display profile
• Attractive geological pattern on both sides
• One-of-a-kind sedimentary mineral formation
• Exact specimen pictured

Perfect for collectors of septarian nodules, Madagascar minerals, fluorescent minerals, UV-reactive specimens, calcite, polished slabs, sedimentary formations, natural stone décor, geological displays, and distinctive cabinet specimens.

Professionally packaged and shipped from Colorado.

You will receive the exact specimen shown.

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