Name/Title
Heulandite / ApophylliteEntry/Object ID
2009.62.59Description
Chemical Composition: see description
Crystal System: Monoclinic System
Description: Common Name: Heulandite / Apophyllite
Chemistry: (Ca, Na)2 - 3Al3(Al, Si)2Si13O36 - 12H2O, Hydrated Calcium Sodium Aluminum Silicate / (K,Na)Ca4Si8O20(F,OH) - 8H2O, Hydrated Potassium Calcium Sodium Silicate Fluoride Hydroxide
Group: Silicates
Location: Jalgaon, India
Description: Grouping of translucent white crystals with two seperate areas of magenta to burnt red crystals mixed with them.
Physical Characteristics of Heulandite:
Color is colorless, white, gray, green, pink, yellow, red, brown and black.
Luster is vitreous to pearly on the most prominent pinacoid face and on cleavage surfaces.
Transparency: Crystals are transparent but most commonly translucent.
Crystal System is monoclinic; 2/m
Crystal Habits include blocky crystals described as diamond-shaped, trapezoidal and old fashioned coffin shape with the two faces of a pinacoid usually prominent. Crystals are often modified by secondary faces with pairs of triangular faces very common. Prismatic and acicular forms are also known and are difficult to identify as heulandite. In aggregate specimens this face can be oriented upward producing a crust of curved pearly faces or it can be oriented to the side where the tops of the crystals jut out like the roof tops of a suburban community. Crystals can be simple or complexly modified by a variety of prism and pinacoid faces.
Cleavage is perfect in one direction parellel to the prominent pinacoid face.
Fracture is uneven.
Hardness is 3.5 - 4, maybe softer on cleavage surfaces.
Specific Gravity is approximately 2.1 - 2.3 (very light due to the open channels and high water content).
Streak is white.
Associated Minerals are extensive and include quartz, calcite, apophyllite, barite, pyrite, prehnite, pollucite, tourmaline, scolecite, analcime, chabazite, ferrierite, mordenite, laumontite, natrolite, stilbite and other zeolites.
Best Field Indicators are crystal habit, density, cleavage, luster and associations.
Physical Characteristics of Apophyllite:
Color is clear, white, green, yellow, pink, violet or rarely brown.
Luster is vitreous to pearly on cleavage surfaces.
Transparency: Crystals are transparent to translucent.
Crystal System is tetragonal; 4/m 2/m 2/m; natroapophyllite is orthorhombic, 2/m 2/m 2/m.
Crystal Habits include four sided prisms (with a square cross-section) truncated with either a steep four sided pyramid or a pinacoid termination or both. If the pyramids are missing, the crystals can look cubic. Rarely are the prisms missing, but if they are, crystals could appear octahedral because of the four sided pyramids. The faces of the pyramids do not lineup with the prism faces but with their edges, therefore the pyramid faces have four edges and appear diamond shaped instead of triangular like the pyramid faces of quartz. Rare tabular hydroxyapophyllite crystals are also known.
Cleavage is perfect in one direction (basal).
Fracture is uneven.
Hardness is 4.5 - 5.
Specific Gravity is approximately 2.3 - 2.4 (lighter than most translucent minerals).
Streak is white.
Other Characteristics: Prism faces are striated lengthwise, some specimens are fluorescent and crystals will flake when heated.
Associated Minerals are prehnite, quartz, heulandite, stilbite, natrolite, analcime, datolite, babingtonite, cavansite, calcite, idocrase, wollastonite, kinoite, gyrolite and many other zeolites.
Best Field Indicators are crystal habit, striations, associations, environment of formation, cleavage and luster on cleavage surfaces.
Fracture: conchoidal
Hardness: 4 Flourite
Luster: Vitreous
Occurrence: Heulandite forms large crystals in the petrified bubbles (called 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 in those
situations.
Apophyllite is typically found as secondary minerals in holes in basalt or other igneous rocks.
Rock Type: Igneous
Specific Gravity: 2.2
Streak: white
Variety: Heulandite is one of the most common and one of the most well known members of the Zeolite Group. It can have a nice pearly luster and lovely colored hues. It forms wonderfully complex and quite unique crystals and is often associated with other rare and beautiful minerals.
The name apophyllite is derived from the Greek apophylliso, meaning "it flakes off," a reference to this class's tendency flake apart when heated, due to water loss and refers to a specific group of phyllosilicates, a class of minerals that also includes the micas.Collection
RAGM Mineral CollectionAcquisition
Accession
2009.62Source or Donor
Museum Collection of MineralsAcquisition Method
DonationDimensions
Width
4 inDepth
1-1/2 inLength
6 inWeight
1.65 ozDimension Notes
Dimension taken at widest pointsLocation
Location
Display Case
DS-6Room
Delmar Smith HallBuilding
Crater Rock MuseumCategory
PermanentMoved By
Curtis GardnerDate
May 24, 2023Notes
Added current locationLocation
Container
RightDrawer
2nd shelfShelf
left, leftWall
South wallRoom
Delmar Smith HallBuilding
Crater Rock MuseumCategory
PermanentMoved By
scottDate
September 19, 2009Location
Container
CenterDrawer
Top shelfShelf
LeftCabinet
Case #41Wall
South wallRoom
Delmar Smith HallBuilding
Crater Rock MuseumCategory
Permanent