HARMOTO ME. 
zircon, from which, vill it is perfectly diftinG, not 
only by the cleavage of the cry’ ftals, its fpecitic gravity » XC. 
but particularly, as later analyfes have fhewn, by its chemi- 
cal compofition. 
Le colour of the harmotome is _greyith-white, | ee, 
milk- 
according to 
of ifofceles triangles, 
planes that may be tup- 
pofed to pafs through the edges which meet at the fummit, 
ra throug o ’ 
in a memoir on this fubje@t, read before the Linnzan Society 
of Leipzig, as early as the year £793) confidered the nucleus 
of the crofs-ltone to be arhomboid, two _ whofe angles he 
computed to be between 92° a “the two others 
between 7o’ and 88 This opinion, finda on the direc- 
tion of the ftriz obfervable on the acuminating planes of. the 
cry ye has Hace been objected to , partly on account of its 
different modifications ef the 
Seitible in the “direction of the ftrie of t Fiat es. But 
the latter of thefe objections would be splice alfo to the 
cryftals of ‘other fabikaricee; fach as the itriated o¢tahedrons 
of oxyd of tin, &c. which are equally indivifible in the 
t ha 
but too frequent! 
ieee that the ery eee ty i 
uft hav 
redan ngular 
i em in the defcription of the berate cry ftal 
nitherto noticed. 
I. Simple Cryftallization. 
1. The dodecahedron, with rhomboidal planes. The 
angles of the eight planes, fuppofed to be parallel to thofe 
Haufmann, of 72° 5' 54”, 
bevilled at the diet 
This modification is formed by the eee of lamine 
s arge at the ex- 
“oahers, which fometimes even even difap- 
"The scbvabaial Four-Sided prifm, terminated = = ing § c 
ae by fix planes, four of which are 
_ gdges (bein being the former modification), sid two on two op 
" others of 67° 2 
' (thofe of the Hartz are feldom found fimple,) the Ha 
thi 
he originate by a fimple decrement of shi ston: a at 
both fides ; the four lateral planes Ss HERE before, 
octagons with four angles of 1 ex 
of 
the Lee hae planes depends 
truncating pon 
e magnitude of 
5) 
an angle tar 42" ees aan é rhomboidal ter- 
minal ‘planes under one of 1 8 <3", 
If thefe truncating planes encreale to fach a de egree as to’ 
make the rhomboidal terminal planes lilapoie the i 
reprefent 
4. The rectangular enters prifm bevilled i two 
extremities. (Buch Kreutz ig. 11.) Two the 
lateral planes are recta neil the two others 
with the two angles of 112° 37/12", and four others of 
126° 52'4". ‘The height of the prifm is often coutdersly 
diminifhed 1 in proportion to the other dimentions ; fometime 
to fuch a degree, that the two reCtangular lateral ame 
difappear entirely, in which cafe this variety pafles into the 
. Oblique four-fided prifm, whofe fides are analogous to, 
the bevilling planes of var. N° 4, and the ends to the two ran 
fided lateral planes of the preceding modifications Hence 
it has two of its lateral edges of 112° 37’ 12", 
2' 48" 
Il. Twin-Cryftals. - 
‘Thefe beitis much more common than the fimple cry ftals, 
tome were! the name crofs-ftone b 
ki 
Thefe twin cryftals are not always of the fame it ; the 
more common are thofe compofed = se of the dodecahedral 
cryftals No. 2, that are wider 
other, and a ak each other longitudinally 
have a common axis. 
‘arm 
7) Alfo Var. Nos. ly » 
4 B00, 59 Oe. 
2°$, diene var. : Noe 3 as likewife of var, Ne} 
ah var. N° 5, in. — combination the priim N ey BS 
oe origin, and halves of N“5 are placed on its its broader 
In the prifnatic twin cr ptala, ¥ one of the halves of the 
condary prifms is fometimes wanting, oftener ent Bos 
fea on both fides, and commonly placed ef in the 
planes of the primary hfe a 
wo halves on one or bot broader planct 
cowards their middle, 
The fize of the cryftals. varies varies from 
. fearcely the fourteenth part of an inch: ane at 
pera pho are thofe of Strontian 5 eS minute ery ; 
mnted Arias namely, one 
a longitudinal ri, with lateral ievise Ta diced wag eiy 
4", and four others’ 
2". The ~ proport: on of the fides of thefe oa 
on 
Thefe meet ct re lateral planes fat 
hexagon 
