The following images are taken from a Samsung S III phone (Yes, you can’t believe the quality of detail on these images came from a 8 pix camera; contact me for technical/electronics detail on that) during the lab periods for Geology 311 (Mineralogy and Rocks) Winter 2013 at the University of Calgary.
Please click on the image on the left to access the larger original file. Download the PDF Version here.
Igneous and Precipitate Minerals and Rocks
Sample
Properties
Biotite
Chem: K(Fe,Mg)3AlSi3O10(OH)2 Type: Sheet / Phyllosiclicate Structure: T-O-T+c structure Comp. Anio: (Si4O10)4- Si-to-O: 2 ; 5 Cry. sys: Monoclinic Hd: 2.5 / 3.0 Hs: shiny black Col/pleo: tan/straw brown – dark brown or green – brown green Relief: moderate/+ve Cleve: perfect cleavage Twin: none Habit: massive/platy Ext: parallel / pebbly Int. col: 3rd – 4th Other: vitrous
Calcite
Chem: CaCO3 Type: rhombohedral / trigonal Hd: 3 Hs: Colourless, white, grey colourless, maybe dirty Relief: high/positive Cleve: brittle / concoidal black with pastel stripes Twin: wiggly twins?!? Habit: crystalline/granular Ext: twinkling extinction Int. Col: VERY HIGH – 4th order Other: reacts readily with HCl
Chromite (alt)
Chem: FeCr2O4 Hs: brown streak, metallic luster, black granular Other: black under both xpl and ppl
Garnet
(Ca,Fe,Mg,Mn)3Al2Si3O12 Orthosilicate / Nesosilicate T-O structure Comp. An: SiO44- Si-to-O: 1 ; 4 Type: isometric / cubic Hd: 6.5 – 7 Hs: red but variety too Col/pleo: clear/dirty – none Relief: high/positive Twin: none/uneven Habit: blocky/cubic Ext: NA
Chem: Ca2(Mg,Fe)5Si8O22(OH)2 Inosilicate Monoclinic moderate/+ve green under PPL
Andalusite
Chem: Al2SiO5 Orthosilicate / Nesosilicate orthorhombic 7-7.5 red? Dark cross-like in x-section = chiasolite Col/pleo: clear/dirty – darker than Cordierite in ppl Relief: moderate/+ve Ext: parallel Int. Col: 1st – grey Other: looks like a dirtier Cordierite, higher relief LOW PRESSURE POLYMORPH
Bedding vs Cleavage
To be updated…
TBA
Blueschist
This rock is formed deep underground about ~15 to 30 km of depth with between ~200 to 500 degrees Celsius. Blue colour is caused by Glaucophane mineral in the rock, which is a type of amphibole.
Chert
Chem: SiO2 Hd: 7 Hs: black, grey, white Col/pleo: dirty brownish grains – none Relief: low/-ve Cleve: none/concoidal Habit: nodules Int. col: 1st – grey/white Notes: not a true mineral rather a siliceous ooze – fine crystalline in xpl. Hardness same as quartz
Chalcedony and cavity filled with quartz
Chalcedony is a type of fibrous cryptocrystalline to fine grained silica that forms in pores, cavities and vugs in pre-existing rocks by precipitation from Si-rich fluids that pass through the rocks. Agate is a more brightly coloured variety of chalcedony that typically shows colour banding, with the colours being due to trace amounts of iron and manganese (or, increasingly, to dyes!). The concentrically banded geodes that you see in rock shops are vugs that have been partially to wholly filled with chalcedony/agate.
Chlorite
Chem: (Mg,Fe)3(Si,Al)4O10(OH)2*(Mg,Fe)3(OH)6 Sheet / Phyllosillicate T-O-T structure Monoclinic Hd: 2-2.5 Hs: green clear – green Relief: high/positive Cleve: perfect cleavage foliated masses – 2nd – Berlin Blue Other: has inclusions
Coal
To be updated…
Dolomite
CaMg(CO3)2 rhombohedral / trigonal Hd: 3.5 – 4 Hs: Colourless, white, grey (due to impurities, it can be many colours) Col/pleo: colourless/none Relief: low-moderate Cleve: perfect Twin: black with pastel stripes, wiggly twins?!? Habit: crystalline/granular Ext: twinkling extinction Int. Col: VERY HIGH – 4th order Other: Sugary texture may only be observed in finely crystalline dolomite as opposed to curved crystals faces of coarse dolomite. HCL reaction is very poor to none. It is extremely difficult to separate dolomite from calcite using a thin section. Precipitate mineral!
Epidote
Chem: FeAl2O-OH[Si2O7][SiO4] Sorosilicate Monoclinic 6 silver/pistachio green yellow or green colourless to greenish yellow Relif: high/+ve brittle – planar lamellar (not common) fibrous, coarse to fine granular, massive. 3rd – bright green vitrous, Notes: pearly (Regional and contact metamorphic rocks)
Garnet with pressure shadows
Please check the information for the mineral in the igneous table above.
Hematite (Ore) (B), Quartz (A)
On the XPL photo, you can see the radiating cement of quartz (A) and the think black-brown (to dark reddish) outline of hematite (B) Hs: red-brown streak, steel gray and metallic shiny
Kyanite
Chem: Al2SiO5 Type: Triclinic Hd: 5.5-7 Hs: blue Col/pleo: clear Relief: high/+ve Twin: simple twins (sometimes) Habit: bladed / tabular Ext: inclined Int. Col: 1st – grey/yellow Other: HIGH PRESSURE POLYMORPH, may show stepped appearance like “tree-bark” in thinsection
Chem: (Fe,Mg,Zn)2Al9(Si,Al)4O20(OH)4 Type: Orthosilicate / Nesosilicate Monoclinic Hd: 7-7.5 Hs: dark brown / black Col/pleo: honey/potato yellow – none (ppl) Relief: high/+ve Cleve: subconcoidal Ext: zoning? Habit: intersecting prisms like a cross Int. Col: 2nd – mid/high yellow Other: poikiloblastic (air bubbles), “stauros” greek for cross – 2intersecting prisms HEXAGONAL SHAPED EUHEDRAL
Tremolite
Monoclinic 5.0-6.0 white, brown… colourless – none moderate/+ve brittle 2@60/120 silky, fibrous 2nd – bright turquoise similar to sillimanite in handsample
Zebra Dolostone
This type of rocks were originally limestone, now transformed into ‘Zebra’ dolomite.
At least partially fracture controlled, because of planar zones of coarse, light-coloured dolomite in darker, fine grained host. However, all of the rock now consists of dolomite, including the dark fine grained portions, suggesting an earlier period of pervasive dolomitization.
Halite and Gypsum
Halite is a Precipitate! Since it is white in colour, hand samples may be contaminated with other minerals causing it to appear in different coulours. The Halite is pretty much table salt, but do not taste it.
Gypsum has a sugary texture, curved crystal surfaces
Clinopyroxene Ca(Fe,Mg)Si2O6 Single Chain / Inosilcate T-O-T structure (SiO3)2- 1 ; 3 Monoclinic 5.0 – 7 shiny black – dull weathered black earthy/brown – nonpleochroic moderate/+ve 2@90 sometimes carlsbad / zoning thin lamellar tabular inclined (35-48) 2nd – low/mid
Apatite Ca5(PO4)3(F,Cl,OH) – – – – Hexagonal 5 very small usually – never see clear/none high/positive none/concoidal none six sided euhedral – 1st – grey/white usually a captured/ looks standing up… looks like quartz but really small
Tourmaline Na(Fe,Mg)3Al6(BO3)3(Si6O18)(OH)4 Ring / Cyclosilicate – Si6O1812- 1 ; 3 rhombohedral / trigonal 7 black hexagonal prisms seen in class? variable – variable moderate/+ve none none striated prism parallel 1st – 2nd – moderate
Cordierite Al2SiO5 Ring / Cyclosilicate orthorhombic 7-7.5 clear/dirty – lighter than Andalusite, has border moderate/+ve subconcoidal sector twinning 1st – grey/white looks like a cleaner andalusite, has patchy domains that extinct at different angles within crystal, has sometimes brown outlined border around crystal
Glaucophane Double Chain / Insolcate Monoclinic 5.0 – 6.0 grey/lavender blue lavender blue to striking blue (ppl) bladed / fibrous 3rd – bright blue
I use cookies to optimize site functionality and improve your experience. By continuing to use this site, you accept the use of cookies stated under Privacy Policy and Terms of Use. Read MoreACCEPT
Cookies
Privacy Overview
This website uses cookies to improve your experience while you navigate through the website. Out of these cookies, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website. We also use third-party cookies that help us analyze and understand how you use this website. These cookies will be stored in your browser only with your consent. You also have the option to opt-out of these cookies. But opting out of some of these cookies may have an effect on your browsing experience.
Necessary cookies are absolutely essential for the website to function properly. This category only includes cookies that ensures basic functionalities and security features of the website. These cookies do not store any personal information.
One thought on “Minerals and rocks from GLGY311 Lab”
Comments are closed.