![]() Tapered, column-like formations are 'stalactitic' or 'columnar' while concentrically banded formations are of 'concretionary' habit. Smaller spherical forms are of 'pisolitic' or 'oolitic' habit ovoid clusters or formations are 'amygdaloidal.' 'Colloform' crystal habits termed 'botryoidal,' 'mamillary,' and 'reniform' display spherical, bulbous or globular lumps. Surface energy relations are also quite important to the direction of crystal growth this process is not yet fully understood.Īdjectives used to describe the habit of individual crystals are 'equant,' 'prismatic,' and 'tabular.' Aggregates of crystals may also be termed equant or prismatic, while aggregates of thin, flat, tabular crystals may be 'bladed.' Thin sheets, flakes or scales are termed 'foliated,' 'micaceous,' and, if feathery or delicate, 'lamellar' or 'plumose.'Ĭrystal aggregates resembling long, slender needles, hair, or thread are termed 'acicular,' filiform,' 'capillary,' or 'fibrous.' An aggregate of crystals forming a network or lattice is 'reticulated ' one composed of branches which radiate starlike from a central point is 'stellated' while a branching and treelike mineral growth is 'dendritic.' ![]() The amount of space available for a crystal to fill affects its final shape and size. Higher environmental temperatures during formation increase ion mobility and aid in crystal formation the rate at which the environment cools determines how much time a mineral is allowed to form large crystals. ![]() The direction from which a growing crystal may obtain such solutions is a factor which will affect its eventual shape. For example, aqueous solutions near or surrounding a crystal contain the elemental substances which it needs to continue growth. Crystal habit is thus often useful in identification.Īlthough each mineral species typically forms according to a few preferred shapes, crystal habit is largely determined by the environmental conditions under which a crystal develops. The crystals of particular minerals species sometimes form very distinctive, characteristic shapes. Scalenohedron Calcite on Dolomite from the Elmwood Mine in Tennessee Naturally formed specimens are rarely quantitatively perfect. Instead, it is intended as a supplement to this system.ĭiscussions of crystal habit are more descriptive than precise for this reason the terminology is suited to the discussion of mineral samples discovered in the field. The terminology used to describe crystal habit is not intended to replace the precise nomenclature of crystallography. Subtle evidence of the crystal system to which a mineral species belongs is, however, frequently observed in the habit of the crystals which a specimen displays. It may bear little relation to the form of a single, perfect crystal of the same mineral, which would be classified according to crystal system. For whatever reason, clear and truly clean gwindel quartz is more uncommon than smoky quartz from Swiss locations.The term crystal habit describes the favored growth pattern of the crystals of a mineral species, whether individually or in aggregate. Contacted on the bottom where it was removed from the alpine cleft. This Gwindel is of large size, has very good balance, and in excellent condition with only trace microchipping on three of the terminations that are barely discernible. This piece just sparkles in a display case in a way that normal Quartz clusters seldom do. There is one doubly terminated Quartz crystal on the backside and then six smaller Quartz crystals at the base on the front along with one partial crystal. For whatever reason, they also seem to be less expensive, not more, though they are just as beautiful! This piece is composed of six recognizable, imbricated, limpid and twisted Quartz crystals, two of which are disctly terminated and all have incipient geometric growth faces along their length as well as slight striations perpendicular to the long axis of the crystals. It seems that clear gwindels such as this are much more uncommon than the traditional Smoky Quartz Gwindel specimens. A sparkling, water-clear, gem Quartz specimen showing a dramatic Gwindel (twisted) growth, totally characteristic of the occurences in the high Swiss Alps.
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