ORYCTOGNOSY. 
lamellar ; and again either quite ftraight, as in fome varieties 
nd barytes, or fortification-like, as in amethyft : 
r, which i 
d conica -concentric, 
as in amethytt 
2 of ar an inch 
: h 
a Oe “Thickoils juft aia by the 
naked pied as in native arfenic and brown 
ar denominate thofe diftin& ae ee in which 
d thicknefs are inconfiderable in comparifon 
th; thefe, lie refpe& to dire€tion, are ftraight 
us {par; and curved columnar, as 
With ‘regard to thicknefs, they are very 
thick columnar, as in quartz and calcareous fpar; thick 
columnar, as in ealcareous fpar and amethyfl; thin columnar, 
as in clay iron-ftone; very thin columnar, as in amet 
> 
+ 
yrite 
ferent fizes of the fame variety of diftinét concretions, occur 
together, ae oe one including the other, or the one tra- 
_ ng the 
The Surface a the di a Concretions. —This is {mooth, 
as in hemat rough, in clay iron-ftone ; ftreaked, 
heh is citer longitudinally ftreaked, as in fhorl, “sari aael 
as in calcar tran fverfely, as in amethy tt ; 
even, as in ee own 
3. The Luftre of the dj hiftin&t pas le which is deter- 
mined in the fame manner as the external luftre. 
IV. The general AfpeG. _This comprehends the trapf- 
re. the ftreak, and the foilin 
heTran/par. ency, whichis diftinguithedi into tranfparent ; 
which | is again either fimply tranfparent, or doubly tranf- 
in pitch-ftone, granular lime-ftone ; tranflucent at the edges, 
asin ae heliotrope ; opaque, as in chalk, &c. 
treak, which is either of the fame colour as in 
chalk, more or lefs different: thus crimfon red cinnabar 
vids a Matera ftreak ; aurora red orpiment, an orange- 
ellow ftreak. Molt native metals have their luftre in- 
creafed by the ftreak. 
3 
he Tenacity.—Its degrees are ; brittle, when the ye 
ike are in the higheft degree coherent and immoveable, 
n quartz, grey copper ore; fedtile, when the particles are 
coherent, but not perfeétly immoveable among one another, 
as in galena; malleable or — when the integrant a 
ticles are coherent, and alfo m or ay mo oveable amo 
one anot ge as in moft of the n es ive m 
nto common, 
Pibiten atch is diftingui 
ner aus as in 
as in ete minerals, amianth, &c. ; 
he Adhefion to Sei it oo to which minerals 
oath this property ftrongly, as hydrophane opal; rather 
at 2 as bole ; eis as talc; very weakly, ag cla : 
1. Charaéters for the Hearing. — The Sound. iti is ringing 
or founding, as in native arfenic; creaking, as in native 
amalgam when preffed with the finger ; grating or ruftling, 
as in pafling the finger over mountain cork and mealy 
— 
articular generic CharaGers of Friable Minerals.—The 
Preteen included under this article are, the external form, 
the luftre, the appearance of the particles, the ftain, and the 
fri ough 
The external Form.— According to ca friable mine- 
ah sare maflive, as porcelain earth ; nated. as blue 
iron earth ; thinly coating, as aie espe ore; {purious, 
as fcaly brown iron-{tone, or a fro den- 
wn 
ritic, as earthy and gre -y ma aganele or 
is determined as in folid mine cals 
either mon gli 
metallic ee as in brown iron froth; pearly alin: 
ering, as in ed talc ; I, as in earthy cobalt 
ochre, &c. The a ape of the particles, which are either 
uft-like, as in porcelain earth; or fealy, as in talc 
earth, chlorite earth. 4. The Jalings 0 or fain, which is either 
ftrong, as in iron froth; or flight, as in black cobalt ochre. 
. The friability, with regard to as ich, the particles of 
friable minerals are either loofe, that is, when t ey have no 
perceptible ie aaa as in blue iron earth; or cohering, 
as in cobalt cruft. 
Particular goer Charaders of Fluid Minerals—In thefe 
Werner confiders, 1. e lu uftr é, which is — —— 
as in mercury ; or refi inous, as in petroleum. e tranf- 
eee tranfparent, as in naphtha ; and, as in cae: 
opaque, as in mercury. 3. The fluidity ; aad as 
P 
jn mean. $ vifcid, as in mineral tar. 
Remaining common generic external Chara@ers. 
1. The Un&uofii eh of which thereare four degrees, viz. mea- 
gre, as is the cafe moft minerals; rather greafy, as pipe 
, 8 Aiea as Faller? searthand fteatite; very greafy, as talc. 
2. The Coldne/s, which includes shree degrees, viz. cold, 
fuch as eae jafper, porphyry ; rather cold, as — 
gypium ; flightly cold, as amber. By this character, c 
and polifhed ones may often be diftinguifhed, as alfo real 
gems, from thofe which are artificia 
3. The Weight.—In order to demas with accuracy 
the {pecific gravity of minerals, a ee balance is made 
ufe of ; but w n this cannot be had recourfe to, a mineral 
