DATOLITE and APOPHILLITE, POONA, INDIA (large cabinet)

Datolite is a calcium boron hydroxide nesosilicate with the chemical formula CaBSiO4(OH). It was first identified by Jens Esmark in 1806, who named it from the Greek words δατεῖσθαι, meaning "to divide," and λίθος, meaning "stone," reflecting the mineral's granular structure. 

This mineral crystallizes in the monoclinic system, resulting in prismatic crystals and nodular formations. It exhibits a vitreous luster and can appear in various colors, including brown, yellow, light green, or colorless. Datolite has a Mohs hardness of 5.5 and a specific gravity ranging from 2.8 to 3.0.

Apophyllite designates a specific group of phyllosilicates, which are a category of minerals. Initially, this term referred to a single mineral but was redefined in 1978 to encompass a class of minerals with similar chemical compositions that form a solid solution series, including fluorapophyllite-(K), fluorapophyllite-(Na), and hydroxyapophyllite-(K). The term apophyllite is derived from the Greek word apophyllízo (ἀποφυλλίζω), meaning 'it flakes off,' highlighting the tendency of these minerals to disintegrate upon heating due to water loss. Exfoliation can also occur through acid treatment or simple abrasion. These minerals are commonly found as secondary formations within vesicles of basalt or other volcanic rocks.