sulfides 9-12 SET 3 Flashcards
Realgar formula
As4S4
Realgar crystal form
- monoclinic, uncommon crystals
- coarse to fine grained earthy encrustations
Realgar cleavage
pinacoidal good
Realgar hardness
1.5 to 2 sectile
Realga specific gravity
3.48
Realgar color
resinous, transparent to translucent. red to orange and red to orange streak
Realgar occurrence
- in hydrothermal veins with orpiment
- assoc with lead and silver minerals and well as stibnite
- as volcanic sublimation product
- deposit from hot springs
Realgar remarks
red color, orange red streak, resinous luster and invariable assoc with orpiment
orpiment formula
As2S3
orpiment crystal form
- monoclinic, rare crystals
- usually foliated, columnar, or fibrous masses
orpiment cleavage
pinacoidal perfect 010. flexible cleavage laminae, not elastic
orpiment hardness
1.5 to 2 sectile
orpiment specific gravity
3.49
orpiment color
resinous translucent. lemon yellow, pale yellow streak
orpiment occurrence
- rare mineral
- assoc with realgar, formed same conditions
orpiment remarks
- yellow color
- foliated structure
- excellent cleavage
how to differentiate orpiment and sulfur?
orpiment has perfect pinacoidal cleavage, sulfur has none, only conchoidal fracture.
also orpiment is sectile, sulfur is brittle
stibnite formula
Sb2S3
stibnite crystal form
- orthorhombic common crystals
- slender prismatic, with vertical striations in prism zone, the prisms appear bending or twisted bc of translation gliding
- often in radiating crystal groups or bladed forms with prominent cleavage
- massive coarse to fine granular
stibnite cleavage
perfect pinacoidal 010, paralle striations 100
stibnite hardness
2
stibnite specific gravity
4.52 to 4.62
stibnite color
metallic opaque. (very color on cleavage).
lead gray to black, same with streak
stibnite occurrence
- in low temp hydrothermal veins or replacement deposits
- in hot spring deposits
- in assoc with other antimony minerals that formed as a product of its decomposition, with galena cinnabar, sphalerite, barite realgar orpiment and gold
stibnite remarks
bladed habit, perfect one direction cleavage, lead gray color, soft black streak
stibnite remarks
bladed habit, perfect one direction cleavage, lead gray color, soft black streak
how to distinguish stibnite from galena
stibnite has a perfect pinacoidal cleavage, galena has perfect cubic.
it also is orthorhombic while galena is isometric
stibite also has lower specific gravity
how to distinguish stibnite from galena
stibnite has a perfect pinacoidal cleavage, galena has perfect cubic.
it also is orthorhombic while galena is isometric
stibite also has lower specific gravity
pyrite crystal form
- isometric, striated cube faces, pyritohedron, octahedron
- massive, granular, reniform, globular
pyrite cleavage
none. conchoidal fracture, brittle
pyrite hardness
6 to 6.5
pyrite specific gravity
5.02
pyrite color
pale brass yellow, darker because of tarnish. streak greenish to brownish black
pyrite occurrence
- formed in high and low temperatures
- as magmatic segregation, accessory to igneous rocks, contact metamorphism and hydrothermal veins
- common in shales and limestone
- in vein deposits assoc with many mineral esp chalco, sphalerite and galena
how to tell pyrite from gold
pyrite is paler in color, and also harder and brittle
how to tell pyrite from marcasite
marcasite is even paler in color, marcasite is also orthorhombic while pyrite is isometric
what mineral is easily altered from pyrite and what often results because of this?
limonite, often pseudomorphism results
usually there is a capping of limonite in pyrite veins, what’s this called
gossan
