QUARTZ-PORPHYRY 



QUATERNARY 



521 



clear red and sometimes yellowish ; Plasma, green ; 

 Heliotrope or Bloodstone (q.v.), green with red 

 spots. Catholong is a dull milk-white and some- 

 times porous chalcedony, but is regarded by some 

 mineralogists as a variety of opal. Mocha-stone or 

 Moss-agate is a colourless chalcedony, containing 

 brown moss-like dendritic inclusions. Agate (q.v.) 

 consists of alternate layers of chalcedony arid other 

 varieties of crystalline and amorphous silica. Onyx 

 is composed of even layers of black or brown and 

 white chalcedony ; while in Sardonyx, which has a 

 similar structure, the alternate layers are red and 

 white. For amorphous forms of silica which con- 

 tain variable quantities of water, see OPAL. 



Quartz is the most abundant and widely diffused 

 of all rock-forming minerals. It is an import- 

 ant and characteristic ingredient of acid igneous 

 rocks, such as granite, quartz-porphyry, &c., and 

 forms one of the principal constituents of gneiss. 

 In many other igneous and schistose rocks it is 

 met with as a more or less prominent constituent. 

 It occurs also abundantly as a secondary mineral 

 or alteration-product in igneous and schistose 

 rocks generally sometimes irregularly diffused, 

 at other times occupying; cracks, crevices, cavities, 

 &c. Many rocks, especially Arch.nean and Palae- 

 ozoic rocks, are traversed by veins of quartz, which 

 vary in breadth from mere lines up to many feet. 

 In some places such veins are more or less impreg- 

 nated with gold indeed quartz- veins may lie looked 

 upon as the chief repositories of the precious metal 

 (see GOLD). 



Quartz, in crystals, is also one of the most 

 common minerals met with lining the walls of 

 metalliferous lodes. Amongst derivative rocks it 

 plays an important part conglomerates and sand- 

 stones being composed as a rule chiefly of siliceous 

 materials. Chalcedony as a rock-constituent is a 

 product of alteration, and is met with commonly 

 in the vesicles and pores of many igneous rocks, 

 or as irregular aggregates diffused through their 

 ground-mass. It is also a common vein-mineral 

 the coloured chalcedonies especially occurring in 

 this form. Agates occur in veins, and especially 

 in the amygdaloidal cavities of igneous rocks. 



Quartz-porphyry, an igneous rock, consist- 

 ing of crystals of quartz and felspar scattered 

 porphyritically through a compact or very finely 

 crystalline ground-mass of the same minerals. It 

 occurs both as an intrusive rock and in the form of 

 lavas which have flowed out at the surface. Some 

 of the quartz-porphyries which have a very compact 

 or microfelsitrc ground-mass appear to have been 

 originally volcanic vitreous rocks the glass having 

 snlfsequently become devitrified. The non-porphy- 

 ritic varieties which have a flinty or hornstone-like 

 aspect are called Felsite (q.v.). ' Quartzlers-por- 

 pliyry ' is a name for Orthoclase-porphyry (q.v.). 



Quartz-rock, or QUARTZITE, is a commonly 

 occurring rock, composed of an aggregate of quartz- 

 grains welded together. It is usually white, gray, 

 or rusty yellow or reddish in colour, and has a 

 splintery fracture. Under the microscope the grains 

 snow a rounded and often semi-fused appearance, 

 as if they had been mutually agglutinated while 

 in a softened condition. The siliceous paste in 

 which the granules are frequently set has usually 

 a crystalline texture, and now and again crystals 

 of quartz are developed in it. The rock not infre- 

 quently shows false-bedding, and occurs in strata 

 of variable thickness, often forming mountain- 

 masses. Sometimes it assumes a foliated structure 

 (Quartz-schist), and contains scales of mica which 

 occasionally form layers or laminie. The rock 

 is obviously of sedimentary origin, and has sub- 

 sequently been subjected to metamorphic action. 



Quartz-trachyte. See LIPABITE. 



Quasimodo Sunday. See Low SUNDAY. 



Quassia, a genus of trees and shrubs of the 

 natural order Simarubacese (q.v.); having herma- 

 phrodite flowers, with five petals combined into a 

 tube, and much longer than the small calyx, ten 

 stamens, five germens, and only one style ; the 

 fruit composed of rive drupes. Quassia amara is a 

 native of the tropical parts of America and of some 

 of the West India Islands. It is a shrub 10 to 

 15 feet high, with racemes of bright-red flowers, 

 and large pinnate leaves, the stalks of which are 

 remarkably winged and jointed. The wood, and 

 particularly that of the root, has a strong, purely 

 bitter taste, and was at one time much used in 

 medicine under the names of Quassia-wood, Bitter- 

 wood, &c. The flowers were valued in Surinam 

 for their stomachic properties as early as the 

 beginning of the 18th century; the worn! of the 

 root began to be known in Europe before the 

 middle of that century, and was more fully brought 

 into notice about 1756, by Kolander, a Swede, who 

 had visited Surinam, and had learned its value 

 from a negro, called Quassi, Quasha, or Quacy. 

 This negro had discovered it about 1730, and 

 had employed it with great success as a remedy 

 for fevers, so that though, as Rolander says, a very 

 simple man, he had acquired a great reputation 

 by his use of it. Linna-iis published a dissertation 

 on it in 1761, and it was he who gave to the genus 

 the name Quassia, from the name of the slave by 

 whom its medicinal qualities had been made 

 known. The true quassia is now, however, little 

 used ; its name 

 having been 

 transferred to the 

 Bitter-wood (q.v.) 

 of the West 

 Indies, Picr&na 

 (or Quassia) ex- 

 celsa, a lofty tree, 

 the wood of 

 which possesses 

 the same proper- 

 ties, although in 

 an inferior de- 

 gree ; but this 

 inferiority is 

 compensated by 

 the greater facil- 

 ity with which 

 any requisite 

 supply is 

 obtained. It ia 

 the wood of this ' 

 tree which is now 

 sold as Quassia- 

 wood, or Quassia- 

 chips, in the 

 shops. It is used 

 to a considerable 

 extent instead of 

 hops for making 

 beer, although the use of it is illegal in Britain, 

 and beer made with it is said to become muddy 

 and flat, and not to keep. Quassia-wood is very 

 feebly narcotic, and a decoction of it is used for 

 killing flies. Cabinet-work made of it is safe from 

 all attacks of insects. In medicine it is a valuable 

 stomachic tonic ; but in fevers it is not to be com- 

 pared in efficacy with cinchona and its alkaloids. 

 Its proj>erties depend on a bitter principle called 

 quassiin, C,,,H| 2 O3, which is present in minute 

 amount in the wood. 



Quaternary, or POST-TERTIARY, the fourth 

 great division or the fossiliferous strata, which 

 mbraces the Pleistocene (q.v.) or Glacial and Posfc- 

 ;lacial (q.v.) and Recent systems. 



Quassia : Bitterwood ( Picrcena 

 excelsa), branch with bisexual 

 flowers : a, fruit. 



( Bentley and Trimen.) 



