322 Prof. A. H. Church — Specific Gravity of Precious Stones. 



I believe the specific gravity of white, yellow, and blue sapphire 

 is rather over 4 when the specimens examined are perfectly free from 

 flaws. 



No. Name. Remarks. Spec. Grav. 



35. Spinel. ... Indigo coloured, flawless 16° 3-675 



36. ,, A similar specimen 3-715 



37. ,, Puce coloured, flawless 3-637 



38. * ,, Eose coloured, flawless 3-631 



Red, pink, and pale spinels are, I have found, rather less dense 

 than the deep blue and greenish blue stones. The specific gravity 

 of this species is very close to that of the hyacinthine garnet. 



39. Topaz White, flawless, from Brazil 3-597 



40. „ "White, flawless 3571 



41. „ White, flawless 3-585 



42. „ White, slightly flawed, from Brazil 3-564 



43. „ White, flawless- weight 4-369 grams 3-572 



44. „ White, flawless 3-595 



45. „ White, flawless 3-597 



46. „ Wine-yellow, flawless 3 539 



47. „ The same crystal after ignition and change of 



colour to pink 3'533 



48. „ Deep pink, flawless. Had heen heated ; weight 



—2-289 grams 3-534 



49. „ Pale sky blue, flawless 3-541 



The very brilliant white topazes from Brazil have (so far as my 

 experiments have gone) a slightly higher specific gravity than the 

 stones of less lustre from Flinders Island and other localities. Coloured 

 topazes also, from all localities, appear to be less dense than those 

 without colour. Heating, which changes the yellow colour of a 

 topaz to a rose pink, effects no alteration in its density. 



50. * Tourmaline. Green, flawless, from Brazil 17° 3*154 



51. ,, Grass-green, flawed 2-89 



52. „ Black, from Bovey Tracy 3-124 



53. „ Black, Bovey Tracy 3-12 



54. ,, Dull greyish green, flawless 3 303 



55. ,, Green, very slightly flawed 3-109 



Black tourmalines are occasionally miscalled garnets. 



56. Ziecon. ... Brownish yellow, transparent, flawless 4-679 



57. ,, Jacinth from Expailly, flawless (unaltered by ig- 



nition) 4-863 



58. „ Greenish, from Ceylon, flawless 4 - 579 



59. ,, The same stone (58) after prolonged ignition ... 4-625 



60. „ Yellow, flawless 4-6 



61. * „ Brownish yellow, flawless 4-62 



62. ,, Brown, flawless 4-696 



63. ,, Dull dark green, slightly opalescent, flawless ... 4-02 



64. ,, Hair brown, transparent but flawed, Fredriks- 



varn 4-489 



65. ,, The same crystal, after prolonged ignition 4*633 



66. ,, Pale brown, opaque, Green Biver, Henderson Co., 



North Carolina 4*54 



67. „ The same crystal, after prolonged ignition 4-667 



68. ,, Deep red, flawless, from Mudgee, New South 



Wales ., 4-705 



69. ,, The same stone, after prolonged ignition 4-7 



70. „ Pale green, flawless, from Ceylon 4-691 



