Thomsonite – Poona, India -Ref 540

Thomsonite is a mineral from the zeolite group, valued for its radiating spheres that range in color from white to orange-brown. Its orthorhombic crystal structure most often develops as fibrous or acicular aggregates, organized into compact spherical formations.

The specimen shown here, collected in 2024 in Poona (India), clearly illustrates these features with an orange spheroid contrasting against a dark matrix and surrounded by small white crystal growths.

The zeolites of Poona have been renowned for several decades and are among the most sought-after by collectors. They are often found in association with other minerals of the same group, such as stilbite or apophyllite. Beyond their aesthetic appeal, these specimens also represent characteristic crystallization processes in basaltic environments, since thomsonite forms in the cavities of cooled lava flows.

🟢 Mineral Information

Name: Thomsonite

Type: Zeolite

Chemical formula: NaCa₂Al₅Si₅O₂₀·6H₂O

Crystal system: Orthorhombic

Habit: Radiating spherules, fibrous to acicular aggregates

Luster: Vitreous to silky

Colors: White, cream, orange to orange-brown

Hardness (Mohs): 5 – 5.5

Density: 2.3 – 2.4 g/cm³

Presented specimen: Poona (India), 2024; Width 36mm × height 40mm; Weight 87g (with stand).