Name/Title
Scolecite on FluorapophylliteEntry/Object ID
2009.62.197Description
Description: Common Name: Scolecite
Chemistry: CaAl2Si3O10-3H2O
Class: Silicates
Subclass: Tectosilicates
Group: Zeolites
PHYSICAL CHARACTERISTICS:
Color is clear or white.
Luster is vitreous to silky.
Transparency: crystals are transparent to translucent.
Crystal System is monoclinic; 2/m
Crystal Habits include sprays of thin acicular crystals with slanted terminations. Also occurs in radiating fibrous clusters.
Cleavage is perfect in two directions, prismatic. Cleavage is hard to see due to small crystal size.
Fracture is conchoidal.
Hardness is 5.
Specific Gravity is approximately 2.2 (very light)
Streak is white.
Best Field Indicators are crystal habit, hardness, density and associations.
Common Name: Fluorapophyllite
Chemistry: (K,Na)Ca4Si8O20(F,OH) - 8H2O
Class: Silicates
Subclass: Phyllosilicates
Group: Apophyllite
THE 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.
Best Field Indicators are crystal habit, striations, associations, environment of formation, cleavage and luster on cleavage surfaces.
Occurrence: Notable Occurrences include Poona, India; Riverside Co., California; Iceland; Skye Scotland and Santa Catarina, Brazil.
Notable Occurrences are extensive and include the Deccan Traps (ancient basalt flows) in India especially around Poona, also found in Christmas Mine, Arizona; Fairfax, Virginia; Upper Peninsula, Michigan; Oregon; Pennsylvania; Paterson, New Jersey and North Carolina, USA; Rio Grande do Sul, Brazil; Isle of Skye, Scotland; Collinward, Northern Ireland; Mexico; Nova Scotia and Mont Saint-Hilaire, Canada; Iceland; Kongsberg, Norway; Harz Mountains, Germany and Sampo Mine, Takahashi, Okayama, Honshu, Japan.
Variety: Scolecite, a calcium zeolite, natrolite, a sodium zeolite, and mesolite, a calcium and sodium zeolite, are closely related and sometimes found together. The presence of calcium in two of the minerals slightly alters the structure from that of natrolite; from an orthorhombic symmetry to a monoclinic symmetry. However, twinning of scolecite and mesolite often make them look orthorhombic All three minerals are referred to as "chain" or "needle" zeolites. They are similar and hard to distinguish when in clusters with radiating, acicular habits. Natrolite tends to forms thin crystals with pyramidal terminations, but mesolite's fibrous crystals are usually the thinnest crystals of the three minerals. Scolecite's larger crystals tend to be more robust and durable. These characteristics are only generalities and can not be used as dependable identifying traits. Absolute identification can not be made by ordinary means.
Fluorapophyllite is by far the most abundant and colorful of the three and is usually what is referred to when a specimen is just labeled apophyllite. Hydroxyapophyllite is also relatively common, but specimens typically lack any color and are limited to pseudo-cubic crystal habits. The natroapophyllite is quite rare and is found at only a few localities. Its typical brown color can help distinguish it from its close cousins. Natroapophyllite, by virtue of its more significant chemical and symmetrical difference, is truly a distinct mineral. Fluorapophyllite and hydroxyapophyllite however are a different story. The two are different minerals only because of the difference in the percentage of fluorine to hydroxyl ions. They represent the end members of a series that could be called the apophyllite series. The name apophyllite persists however and its usage is widespread, especially when distinguishing the true identity of specimens is difficult. Most mineral guide books list apophyllite as a single mineral and the rest of this discussion will deal with apophyllite in general.Collection
RAGM Mineral CollectionAcquisition
Accession
2009.62Source or Donor
Museum Collection of MineralsAcquisition Method
DonationLocation
Location
Display Case
DS-6Room
Delmar Smith HallBuilding
Crater Rock MuseumCategory
PermanentMoved By
Curtis GardnerDate
May 24, 2023Notes
Added current locationLocation
Drawer
South side CenterShelf
Middle shelf, Middle shelfRoom
Delmar Smith HallBuilding
Crater Rock MuseumCategory
PermanentMoved By
Joshua EspongeDate
November 13, 2009Location
Container
LeftDrawer
2nd ShelfShelf
LeftCabinet
Case# 41Room
Delmar Smith HallBuilding
Crater Rock MuseumCategory
Permanent
