SPHENE

This article appears in Volume V25, Page 647 of the Encyclopedia Britannica.

Encyclopedia Britannica - Main :: SOU-STE

SPHENE , a

mineral

MINERAL

consisting of calcium titan-silicate, CaTiSiO5, crystallizing in the monoclinic system. The crystals vary considerably in habit, but are generally thin and wedge-shaped; hence the name sphene, from the Greek a v (a wedge), given by R. J. Hauy in 18or. The earlier name titanite, given by M. H. Klaproth in 1795, is also in common use. Twinning on the ortho-pinacoid is not uncommon.
The colour is green, yellow, brown or black, and the lustre resinous to adamantine; crystals are transparent to opaque. The hardness is 51, and the specific gravity 3.5. The refractive indices and the optic axial angle vary considerably with the colour of the light: the dispersion of the optic axes is inclined, and the interference figure seen in convergent light between crossed nicols is very characteristic of the

mineral

MINERAL

. Sphene is sometimes cut as a gem-stone, though it is rather too soft to stand much

wear

WEAR

; owing to its high dispersive power it gives
brilliant flashes of prismatic colours. As small embedded crystals, sphene has a wide distribution as an accessory constituent of many kinds of igneous rocks (granite,

syenite

SYENITE

, trachyte, phonolite, &c.), and also of gneiss, schist and crystalline limestone. Sharply-developed, transparent,

pale

PALE (through Fr. pal, from Lat. palms, a stake, for paglus, from the stem pag- of pangere, to fix; " pole " is from the same original source)

green crystals are frequently associated with adularia, asbestos and quartz in the crystal-lined crevices of the schists of the Swiss and Tyrolese Alps. Large, rough and dark-coloured crystals are found at Arendal and KragerS in Norway, and in granular limestone at Diana in New

York

YORK
YORK (
HOUSE
- HOUSE
- HOUSE (O. Eng. hiss, a word common to Teutonic languages, cf. Dut. huis, Ger. Haus; in
  Gothic
  - GOTHIC
  it is only found in gudhiss, a temple; it may be ultimately connected with the root of " hide," conceal)
OF)
YORK, EDMUND OF
LANGLEY
- LANGLEY, SAMUEL PIERPONT (1834-1906)
, DUKE OF (1341-1402)
EDWARD
- EDWARD
.html">YORK,
EDWARD
- EDWARD
YORK, FREDERICK
AUGUSTUS
- AUGUSTUS (a name 1 derived from Lat. augeo, increase, i.e. venerable, majestic, Gr. Ee0avr6s)
, DUKE OF (1763-1827)
YORK, RICHARD, DUKE

and Eganville in Ontario. A greyish, compact and impure' variety of spheric, known as
" leucoxene," frequently occurs in basic igneous rocks as an alteration product of ilmenite and rutile. (L. J. S.)

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