APATITE

apatite, a widely distributed mineral, which, when found in large masses, is of considerable economic value as a phosphate. as a mineral species it was first recognized by a.g. werner in 1786 and named by him from the greek [greek: apatan], to deceive, because it had previously been mistaken for other minerals, such as beryl, tourmaline, chrysolite, amethyst, &c. although long known to consist mainly of calcium phosphate, it was not until 1827 that g. rose found that fluorine or chlorine is an essential constituent. two chemical varieties of apatite are to be distinguished, namely a fluor-apatite, (caf)ca4p3o12, and a chlor-apatite, (cacl)ca4p3o12: the former, which is much the commoner, contains 42.3% of phosphorus pentoxide (p2o5) and 3.8% fluorine, and the latter 4.10 p2o5 and 6.8% chlorine. fluorine and chlorine replace each other in indefinite proportions, and they may also be in part replaced by hydroxyl, so that the general formula becomes [ca (f, cl, oh)] ca4p3o12, in which the univalent group ca(f, cl, oh) takes the place of one hydrogen atom in orthophosphoric acid h3po4. the formula is sometimes written in the form 3ca3(po4)2 + caf2. mangan-apatite is a variety in which calcium is largely replaced by manganese (up to 10% mno). cerium, didymium, yttrium, &c., oxides may also sometimes be present, in amounts up to 5%. [illustration: fig. 1.] [illustration: fig. 2.] apatite frequently occurs as beautifully developed crystals, sometimes a foot or more in length, belonging to that division of the hexagonal system in which there is pyramidal hemi-hedrism. in this type of symmetry, of which apatite is the best example, there is only one plane of symmetry, which is perpendicular to the hexad axis. the arrangement of the pyramidal faces n and u in fig. 2 show the hemihedral character and absence of the full number of planes and axes of symmetry. fig. 2 represents a highly modified crystal from st gotthard; a more common form is shown in fig. 1, which is bounded by the hexagonal prism m, hexagonal bipyramid x and basal pinacoid c. in its general appearance, apatite exhibits wide variations. crystals may be colourless and transparent or white and opaque, but are often coloured, usually some shade of green or brown, occasionally violet, sky-blue, yellow, &c. the lustre is vitreous, inclining to sub-resinous. there is an imperfect cleavage parallel to the basal pinacoid, and the fracture is conchoidal. hardness 5, specific gravity 3.2. yellowish-green prismatic crystals from jumilla in murcia in spain have long been known under the name asparagus-stone. lazurapatite is a sky-blue variety found as crystals with lapis-lazuli in siberia; and moroxite is the name given to dull greenish-blue crystals from norway and canada. francolite, from wheal franco, near tavistock in devonshire, and also from several cornish mines, occurs as crystallized stalactitic masses. in addition to these crystallized varieties, there are massive varieties, fibrous, concretionary, stalactitic, or earthy in form, which are included together under the name phosphorite (q.v.), and it is these massive varieties, together with various rock-phosphates (phosphatic nodules, coprolites, guano, &c.) which are of such great economic importance: crystallized apatite is mined for phosphates only in norway and canada. with regard to its mode of occurrence, apatite is found under a variety of conditions. in igneous rocks of all kinds it is invariably present in small amounts as minute acicular crystals, and was one of the first constituents of the rock to crystallize out from the magma. the extensive deposits of chlor-apatite near kragero and bamle, near brevik, in southern norway, are in connexion with gabbro, the felspar of which has been altered, by emanations containing chlorine, to scapolite, and titanium minerals have been developed. the apatite occurring in connexion with granite and veins of tin-stone is, on the other hand, a fluor-apatite, and, like the other fluorine-bearing minerals characteristic of tin-veins, doubtless owes its origin to the emanations of tin fluoride which gave rise to the tin-ore. special mention may be here made of the beautiful violet crystals of fluor-apatite which occur in the veins of tin-ore in the erzgebirge, and of the brilliant bluish-green crystals encrusting cavities in the granite of luxullian in cornwall. another common mode of occurrence of apatite is in metamorphic crystalline rocks, especially in crystalline limestones: in eastern canada extensive beds of apatite occur in the limestones associated with the laurentian gneisses. still another mode of occurrence is presented by beautifully developed and transparent crystals found with crystals of felspar and quartz lining the crevices in the gneiss of the alps. crystallized apatite is also occasionally found in metalliferous veins, other than those of tin, and in beds of iron ore; whilst if the massive varieties (phosphorite) be considered many other modes of occurrence might be cited. (l. j. s.) apaturia ([greek: apatouria]), an ancient greek festival held annually by all the ionian towns except ephesus and colophon (herodotus i. 147). at athens it took place in the month of pyanepsion (october to november), and lasted three days, on which occasion the various phratries (i.e. clans) of attica met to discuss their affairs. the name is a slightly modified form of [greek: apatoria = hamapatoria, homopatoria], the festival of "common relationship." the ancient etymology associated it with [greek: apate] (deceit), a legend existing that the festival originated in 1100 b.c. in commemoration of a single combat between a certain melanthus, representing king thymoetes of attica, and king xanthus of boeotia, in which melanthus successfully threw his adversary off his guard by crying that a man in a black goat's skin (identified with dionysus) was helping him (schol. aristophanes, _acharnians_, 146). on the first day of the festival, called dorpia or dorpeia, banquets were held towards evening at the meeting-place of the phratries or in the private houses of members. on the second, anarrhysis (from [greek: anarruein], to draw back the victim's head), a sacrifice of oxen was offered at the public cost to zeus phratrius and athena. on the third day, cureotis ([greek: koureotis]), children born since the last festival were presented by their fathers or guardians to the assembled phratores, and, after an oath had been taken as to their legitimacy and the sacrifice of a goat or a sheep, their names were inscribed in the register. the name [greek: koureotis] is derived either from [greek: kouros], that is, the day of the young, or less probably from [greek: keiro], because on this occasion young people cut their hair and offered it to the gods. the victim was called [greek: meion]. on this day also it was the custom for boys still at school to declaim pieces of poetry, and to receive prizes (plato, _timaeus_, 21 b). according to hesychius these three days of the festival were followed by a fourth, called [greek: epibda], but this is merely a general term for the day after any festival. ape (old eng. _apa_; dutch _aap_; old ger. _affo_; welsh _epa_; old bohemian _op_; a word of uncertain origin, possibly an imitation of the animal's chatter), the generic english name, till the 16th century, for animals of the monkey tribe, and still used specifically for the tailless, manlike representatives of the order primates (q.v.). the word is now generally a synonym for "monkey," but the common verb for both (as transferred figuratively to human beings) is "to ape," i.e. to imitate.