A generic term for class of hydrated silicates of aluminum and either sodium or calcium or both, of the type Na2 O.Al2 O3 .nSiO2 .xH2 O . The term originally described a group of naturally occurring minerals. The natural zeolites are analcite, chabazite, heulandite, natrolite, stilbite, and thomsonite. Artificial zeolites are made in a variety of forms, ranging from gelatinous to porous and sandlike, and are used as gas adsorbents and drying agents as well as water softeners. Both natural and artificial zeolites are used extensively for water softening. The term zeolite now includes such diverse groups of compounds as sulfonated organics or basic resins, which act in a similar manner to effect either cation or anion exchange.
A brass-yellow metallic mineral with dark yellow streak; possibly clausthalite with umangite.
A light and dark green variety of pumpellyite in green pebbles of banded structure; occurs in the Lake Superior region, MI.
A monoclinic mineral, (Fe,Mn)2 (PO4 )F; forms a series with triplite; clove-brown.
A. In ore deposits, the spatial distribution patterns of elements, minerals, or mineral assemblages.
B. A variation in the composition of a crystal from core to margin, due to a separation of the crystal phases during its growth, by loss of equilibrium in a continuous reaction series. The higher-temperature phases of the isomorphic series form the core, with the lower-temperature phases toward the margin. Syn: zonal structure
C. Concentric layering parallel to the periphery of a crystal, shown by color banding, such as in tourmaline, and by differences in optical reactions to polarized light, such as in plagioclase feldspar.
D. In a mineral deposit, the occurrence of successive minerals or elements outward from a common center.
E. The development of areas of metamorphosed rocks that may exhibit zones in which a particular mineral or suite of minerals is predominant or characteristic, reflecting the original rock composition, the pressure and temperature of formation, the duration of metamorphism, and whether or not material was added or removed.
Highly localized melting, usually by induction heating, of a small volume of an otherwise solid piece. By moving the induction coil along the rod, the melted zone can be transferred from one end to the other. In a binary mixture where there is a large difference in composition on the liquidus and solidus lines, high purity can be attained by concentrating one of the constituents in the liquid as it moves along a rod.
Mixed arsenates and oxides of cobalt produced by roasting sulfide ores.
A tetragonal mineral, BiOF ; at Sherlova Gory, East Transbaikal, Russia.
Amorphous cadmium sulfide; greenockite is the crystalline form.
One of the three optic axis (x, y, and z) in a biaxial crystal. The z-axis is the axis of least ease of vibration. Light vibrating parallel to the z-axis travels with minimum velocity and is called the slow ray, the z-ray, and the gamma -ray. The highest index of refraction ngamma , in biaxial minerals is the index of the slow ray vibrating parallel to the z-axis.