Stilbite with Apophyllite

Stilbite with Apophyllite from India

Stilbite

Stilbite is a mineral from the zeolite group that often occurs in fan-shaped aggregates or as crusts of shiny crystals. The mineral has a glassy to pearly luster and varies in colour from white and pink to orange and yellow. Due to its attractive crystal shapes and colours, stilbite is popular with collectors and often associated with other zeolites such as apophyllite and heulandite.

Major deposits include India, Iceland, Brazil and the United States. Stilbite forms in the cavities of basaltic rocks and is formed by hydrothermal processes. Its chemical formula is NaCa₄(Si₂₇Al₉)O₇₂-28H₂O. The hardness is between 3.5 and 4 on the Mohs scale.

Sources:
Mindat.org, Wikipedia - Stilbite

Apophyllite

Apophyllite is a group of phyllosilicate minerals often found in clear, prism-shaped crystals with a glassy to pearly luster. The colour ranges from colourless and white to green or pink, depending on traces of other elements. Because of its distinctive crystal shape and transparency, apophyllite is popular with collectors and is often found in combination with zeolites.

Major deposits include India, Brazil, Germany, Iceland and the United States. Apophyllite usually forms in the cavities of basaltic lavas and other volcanic rocks by hydrothermal processes. Its general formula is KCa₄Si₈O₂₀(F,OH)-8H₂O, and its hardness is between 4.5 and 5 on the Mohs scale.

Sources:
Mindat.org, Gemdat.org, Wikipedia - Apophyllite