Analcime (; from Ancient Greek ἀνάλκιμος (análkimos) 'not strong') or analcite is a white, gray, or colorless tectosilicate mineral. Analcime consists of hydrated sodium aluminium silicate in cubic crystalline form. Its chemical formula is NaAlSi2O6·H2O. Minor amounts of potassium and calcium substitute for sodium. A silver-bearing synthetic variety also exists (Ag-analcite). Analcime is usually classified as a zeolite mineral, but structurally and chemically it is more similar to the feldspathoids. Analcime isn't classified as an isometric crystal, as although the crystal structure appears to be isometric, it is usually off only by a fraction of an angle. However, there are truly isometric samples of the mineral, which makes its classification even more difficult. Due to the differences between the samples being too slight, there's no merit from having multiple species names, so as a result analcime is a common example for minerals occurring in multiple crystal systems and space groups. It was first described by French geologist Déodat de Dolomieu, who called it zéolithe dure, meaning hard zeolite. It was found in lava in Cyclops, Italy. The mineral is IMA approved, and had been grandfathered, meaning the name analcime is believed to refer to a valid species til this day.
A crystal or crystalline solid is a solid material whose constituents are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macroscopic single crystals are usually identifiable by their geometrical shape, consisting of flat faces with specific, characteristic orientations. The scientific study of crystals and crystal formation is known as crystallography. The process of crystal formation via mechanisms of crystal growth is called crystallization or solidification.
In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.
A stalactite is a mineral formation that hangs from the ceiling of caves, hot springs, or man-made structures such as bridges and mines. Any material that is soluble and that can be deposited as a colloid, or is in suspension, or is capable of being melted, may form a stalactite. Stalactites may be composed of lava, minerals, mud, peat, pitch, sand, sinter, and amberat. A stalactite is not necessarily a speleothem, though speleothems are the most common form of stalactite because of the abundance of limestone caves.
Calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on the Mohs scale of mineral hardness, based on scratch hardness comparison. Large calcite crystals are used in optical equipment, and limestone composed mostly of calcite has numerous uses.
Strontianite (SrCO3) is an important raw material for the extraction of strontium. It is a rare carbonate mineral and one of only a few strontium minerals. It is a member of the aragonite group.
A speleothem is a geological formation by mineral deposits that accumulate over time in natural caves. Speleothems most commonly form in calcareous caves due to carbonate dissolution reactions. They can take a variety of forms, depending on their depositional history and environment. Their chemical composition, gradual growth, and preservation in caves make them useful paleoclimatic proxies.
Selenite, satin spar, desert rose, gypsum flower are crystal habit varieties of the mineral gypsum.
Epidote is a calcium aluminium iron sorosilicate mineral.
The matrix or groundmass of a rock is the finer-grained mass of material in which larger grains, crystals, or clasts are embedded.
Petrography is a branch of petrology that focuses on detailed descriptions of rocks. Someone who studies petrography is called a petrographer. The mineral content and the textural relationships within the rock are described in detail. The classification of rocks is based on the information acquired during the petrographic analysis. Petrographic descriptions start with the field notes at the outcrop and include macroscopic description of hand specimens. The most important petrographer's tool is the petrographic microscope. The detailed analysis of minerals by optical mineralogy in thin section and the micro-texture and structure are critical to understanding the origin of the rock.
Dolomite (also known as dolomite rock, dolostone or dolomitic rock) is a sedimentary carbonate rock that contains a high percentage of the mineral dolomite, CaMg(CO3)2. It occurs widely, often in association with limestone and evaporites, though it is less abundant than limestone and rare in Cenozoic rock beds (beds less than about 66 million years in age). The first geologist to distinguish dolomite rock from limestone was Belsazar Hacquet in 1778.
The scapolites are a group of rock-forming silicate minerals composed of aluminium, calcium, and sodium silicate with chlorine, carbonate and sulfate. The two endmembers are meionite and marialite. Silvialite (Ca,Na)4Al6Si6O24(SO4,CO3) is also a recognized member of the group.
Alstonite, also known as bromlite, is a low temperature hydrothermal mineral that is a rare double carbonate of calcium and barium with the formula BaCa(CO
3)
2, sometimes with some strontium. Barytocalcite and paralstonite have the same formula but different structures, so these three minerals are said to be trimorphous. Alstonite is triclinic but barytocalcite is monoclinic and paralstonite is trigonal. The species was named Bromlite by Thomas Thomson in 1837 after the Bromley-Hill mine, and alstonite by August Breithaupt of the Freiberg Mining Academy in 1841, after Alston, Cumbria, the base of operations of the mineral dealer from whom the first samples were obtained by Thomson in 1834. Both of these names have been in common use.
Hornfels is the group name for a set of contact metamorphic rocks that have been baked and hardened by the heat of intrusive igneous masses and have been rendered massive, hard, splintery, and in some cases exceedingly tough and durable. These properties are due to fine grained non-aligned crystals with platy or prismatic habits, characteristic of metamorphism at high temperature but without accompanying deformation. The term is derived from the German word Hornfels, meaning "hornstone", because of its exceptional toughness and texture both reminiscent of animal horns. These rocks were referred to by miners in northern England as whetstones.
Cleavage, in mineralogy and materials science, is the tendency of crystalline materials to split along definite crystallographic structural planes. These planes of relative weakness are a result of the regular locations of atoms and ions in the crystal, which create smooth repeating surfaces that are visible both in the microscope and to the naked eye. If bonds in certain directions are weaker than others, the crystal will tend to split along the weakly bonded planes. These flat breaks are termed "cleavage." The classic example of cleavage is mica, which cleaves in a single direction along the basal pinacoid, making the layers seem like pages in a book. In fact, mineralogists often refer to "books of mica."
Anthodites (Greek ἄνθος ánthos, "flower", -ode, adjectival combining form, -ite adjectival suffix) are speleothems (cave formations) composed of long needle-like crystals situated in clusters which radiate outward from a common base. The "needles" may be quill-like or feathery. Most anthodites are made of the mineral aragonite (a variety of calcium carbonate, CaCO3), although some are composed of gypsum (CaSO4·2H2O).
In geology, boxwork is defined as a honeycomb-like structure that can form in some fractured or jointed sedimentary rocks. If the fractures in the host rock are mineralized, they can become more resistant to weathering than the surrounding rock, and subsequent erosion can produce boxwork structures. In mining geology, boxwork is a set of (typically) quartz-lined cavities, retaining the shape of the dissolved ore minerals, in gossans. In classical geology or mineralogy these mineral casts would not be called boxwork, but would instead be called pseudomorphs, or epimorphs. In cave geology, boxwork is an uncommon type of mineral structure, or speleogen, occasionally found in caves and erosive environments.
Spar is an old mining or mineralogy term used to refer to crystals that have readily discernible faces. A spar will easily break or cleave into rhomboidal, cubical, or laminated fragments with smooth shiny surfaces.
Calcite crystals form on the surface of quiescent bodies of water, even when the bulk water is not supersaturated with respect to calcium carbonate. The crystals grow, attach to one other and appear to be floating rafts of a white, opaque material. The floating materials have been referred to as calcite rafts or "leopard spots".
