68 STBEAK. SECTILITY. FLEXIBILITY.— FRANGIBILITY. some varieties of diamond, become luminous in the ,1 „ 1 n exposure to sun-light. After beinrr honfed i 5 f aftcr strongly, some /these ^e^ ^ phoresemg, but regain it on havino- a oW™ . P los ‘ mitted through them or over their surfaces. ytrans " STBEAK. mineral with a pobtY^ scratching the by rubbing it upon a piece of miln i ^ T n °* to ° hard > required only to ascertain tho S laze d porcelain. Where it is surface will in many caw ffi T ! P owder ' the rough more readily applicable and e ’ bufc the P 01nt will be found diamond will Sch ali usefu !' A writing use occasionally coarser n ' f 6r mmcra 8 > but it will be well to quartz, or a point of hard steeh “ “ fragment of corundum or Hue, 3Sitr^rii POint r ay ^. duCe a rou S bor a smooth it may be either white P°7 der - Wber e powder is produced, of the same tint ,, 5 coloured and, if coloured, it may be of the smooth ° r dlfferent from T1 >o lustre mineral. sometimes greater than that of the The no" 63 ^ ^ distinguished as shining, dull, different fromVt ^ Coloured: the 8ame as the mineral, SF.CTILITY AM) malleability. l,c cul il11 '’ «wit, .«i lmmmcr i >‘ bot! ' ° f lhc ” flexibility. being but few mine Vory bmited application, there these, some as t>d that are capable of being bent. Among without any’tended T 81m P 1 > r flexible . a,ld retain the bend mica is both flexible and* TT' % the ‘ r I>revious state i while are flexible from one bid i i ,lun f als also > 118 Kvnnite, precludes this from >, ^ aild not 80 from another, which racter. m becom ‘«g a generally determinative cha- FBANGIBILITY. renders them^lShTnit t - mt con d‘tion of minerals which Dnttit or gb m very different degrees; and,