If you are fascinated by the hidden structures of our planet, you have likely come across
ANALCIME. This mineral is a compelling subject for study, offering a unique glimpse into the complex chemistry that shapes the Earth’s crust.Whether you are a student identifying a hand sample, a researcher looking for crystallographic data, or a collector curious about a new find, this guide breaks down everything you need to know about
ANALCIME. From its precise chemical formula to the geological environments where it thrives, let’s explore what makes this mineral distinct.
The Chemistry Behind the Crystal
Every mineral tells a story through its chemistry. At its core,
ANALCIME is defined by the chemical formula
Na[Si2AlO6]·H2O.This isn’t just a string of letters and numbers; it represents the precise recipe of elements that nature used to build this specimen. This specific chemical composition is what gives the mineral its stability and dictates how it reacts with acids, heat, or other minerals. It is the fundamental “DNA” that geologists use to classify it within the larger mineral kingdom.
Crystallography: Geometry in Nature
One of the most beautiful aspects of mineralogy is the hidden geometry within every stone.
ANALCIME crystallizes in the
Isometric system.Think of this as the mineral’s architectural blueprint. It dictates the symmetry and the angles at which the crystal faces grow. Digging deeper into its symmetry, it falls under the
Cubic hexoctahedral.
- Point Group: 4/m 3 2/m
- Space Group: Ia3d
Why does this matter? These crystallographic details are like a fingerprint. They influence optical properties—how light travels through the crystal—and physical traits like how it breaks or cleaves when struck.
Internal Structure and Unit Cell
If we could zoom in to the atomic level, we would see the “Unit Cell”—the smallest repeating box of atoms that builds up the entire crystal. For
ANALCIME, the dimensions of this microscopic building block are:
a=13.73Å, Z=16
The internal arrangement of these atoms is described as:
Tektosilicates: tetrahedra are linked into 3-D framework with zeolitic H2O with chains of single connected 4-membered rings of SiO4 & AlO4 tetrahedra connected into leucite-type framework containing 6-, 8- & 12-membered rings; Na & H2O lodged in nonintersecting channels // [111].2 Similar structure to sodalite, having bonds of = strength in 3-D; Na atoms in holes have [6]-coordniation.3 Consists of singly-connected 4-rings, arranged in chains coiled around tetrad screw axes (ANA & Gottardi & Galli, 1985); || chains alternate 41 & 43 screw axes; every 4-ring is part of 3 mutually prp chains, each || to xllographic axis; cages, which contain Na-cations & H2O molecules, occur near where chains interconnect, & each T-site is equivalent to every other T-site, & therefore Si,Al distribution among these sites must be random; Na cations are in centers of these cages, but there are 24 cages in unit cell; therefore, Na cations (gen about 16, but may be from 12 to 17) must also be randomly distributed among cages; H2O molecules fully occupy 16 sites in unit cell; any excess H2O molecules must be randomly distributed in unoccupied Na sites.4 It has long been known that many analcime xl are not optically isotropic, non-cubic; early single xl X-ray diffraction work by Coombs (1955) showed that such xl are indeed non-cubic; Mazzi & Galli (1978) refined structures of 7 diff analcime xl, 5 in tetragonal s.g. I41acd & 2 in orthorhombic s.g. Ibca; most tetragonal xl have a>c, but 1 sample has c>a; Hazen & Finger (1979) determined unit cell dimen-sions of another diff 15 analcime xl many of which are cubic, tetragonal, & orthorhombic; several monoclinic symmetry with [2]-axes || to either pseudocubic [100] or [110] directions, & 1 is triclinic; lower symmetry is result of preferential Al occupancy in some of T-sites; Mazzi & Galli (1978) showed that in tetragonal xl with a>c 2 cages are equivalent & contain most of Na with Al concentrated in nearby T-sites; for tetragonal xl with c>a 2 equivalent cages have less Na & assoc Al than 1/3; in orthorhombic xl all 3 cages have diff Na occupancies & Al in nearby T-sites; because structure of monoclinic & triclinic xl have not been refined, ordering patterns in these xl are not known, but ordering may be similar to that in wairakite; fine lamellar, pseudo-merochedral twinning on {110} is present in all non-cubic xl.5 See “Additional Structures” tab for entry(s).6,7,8a,8b,8cThis internal structure is the invisible framework that supports everything we see on the outside, from the mineral’s density to its hardness.
Physical Appearance (Habit)
When you find
ANALCIME in the field, what does it actually look like? A mineral’s “habit” describes its typical shape and growth pattern.
- Common Habit: Commonly trapezohedral macro crystals; granular, compact, massive
- Twinning: Polysynthetic on {001}, {110}
Twinning is a fascinating phenomenon where two or more crystals grow interlocked in a specific symmetrical pattern. If ANALCIME exhibits twinning, it can be a dead giveaway for identification, distinguishing it from look-alike minerals.
Where is it Found? (Geologic Occurrence)
Minerals are the products of their environment. They don’t just appear anywhere; they need specific conditions—pressure, temperature, and chemical ingredients—to form.
Geologic Occurrence:
In silica-poor intermediate and mafic basalts, phonolites, late hydrothermal solutions, etc.Knowing this context helps geologists reconstruct the history of a rock formation. It tells us whether the rock was born from cooling magma, settled in an ancient ocean, or was transformed by the intense heat and pressure of metamorphism. For more broad geological context, resources like the
U.S. Geological Survey (USGS) provide excellent maps and data.
Related Minerals
No mineral exists in a vacuum.
ANALCIME is often related to other species, either through similar chemistry or structure.
Relationship Data:
Zeolite family; forms series with pollucite and wairakiteUnderstanding these relationships is key. It helps us see the “family tree” of the mineral world, showing how different elements can substitute for one another to create an entirely new species with similar properties.
Frequently Asked Questions (FAQs)
1. What is the chemical formula of ANALCIME?The standard chemical formula for ANALCIME is
Na[Si2AlO6]·H2O. This defines its elemental composition.
2. Which crystal system does ANALCIME belong to?ANALCIME crystallizes in the
Isometric system. Its internal symmetry is further classified under the Cubic hexoctahedral class.
3. How is ANALCIME typically found in nature?The “habit” or typical appearance of ANALCIME is described as
Commonly trapezohedral macro crystals; granular, compact, massive. This refers to the shape the crystals take when they grow without obstruction.
4. In what geological environments does ANALCIME form?ANALCIME is typically found in environments described as:
In silica-poor intermediate and mafic basalts, phonolites, late hydrothermal solutions, etc.. This gives clues to the geological history of the area where it is discovered.
5. Are there other minerals related to ANALCIME?Yes, it is often associated with or related to other minerals such as:
Zeolite family; forms series with pollucite and wairakite.
External Resources for Further Study
For those looking to dive deeper into the specific mineralogical data of
ANALCIME, we recommend checking high-authority databases:
Final Thoughts
ANALCIME is more than just a name on a list; it is a testament to the orderly and beautiful laws of nature. With a chemical backbone of
Na[Si2AlO6]·H2O and a structure defined by the
Isometric system, it holds a specific and important place in the study of mineralogy.We hope this overview has helped clarify the essential data points for this specimen. Whether for academic study or personal interest, understanding these properties brings us one step closer to understanding the Earth itself.
