|
|
www.mineralgallery.co.za Minerals F-J |
|
|
||
Name
Heulandite
Chemistry
(Ca, Na)2 - 3Al3(Al, Si)2Si13O36 - 12H2O, Hydrated Calcium Sodium
Uses
As mineral specimen.
Color
Colorless , white, grey, pink, orange, red or brown; transparent to translucent.
Hardness
3.5 to 4
Specific gravity
2.1 to 2.2
Crystals
Monoclinic 2/m .
Accompanied by:
Zeolite, Stilbite in caveties in basaltic rocks.
Fracture
Fracture is conchoidal to uneven
Luster
Vitreous, pearly on cleavage surfaces.
Cleavage
It is perfect in one direction parellel to the prominent pinacoid face.
Streak
White.
Similar to:
Quartz, calcite, apophyllite, barite, pyrite, prehnite, pollucite, tourmaline, scolecite, analcime, chabazite, ferrierite, mordenite, laumontite, natrolite, stilbite and other zeolites.
Heulandite ( which is s sodium calcium aluminum silicate hydrate mineral), is very widespread and is one of the most well known members of the zeolite family.
It is mainly found in vesicles of volcanic rocks, especially basalts, also metamorphic formation and in deep sea sediments.
Heulandite forms large crystals in petrified bubbles (vesicles) of volcanic rocks that have had a slight amount of metamorphism.
Heulandite occurs in other environments but does not generally form large well shaped crystals.
Natural heulandite specimens can have significant amounts of strontium, potassium, magnesium and barium in the chemical structure.
It some times has a nice pearly luster and beautiful colored hues. It forms amazingly complex and quite exceptional crystals. Heulandite always have a certain depth of translucency.
Its structure is sheet-like. The sheets are connected to each other by a few bonds that are relatively widely separated from each other. Heulandite's sheet-like structure produces the prominent pinacoid faces, the perfect cleavage and the unique luster on those faces.
