OGReNet Lesson Recipes
written by:
David Dillon,
Department of Earth Sciences,
The University of Western Ontario
This is a chart showing the basic properties of
some rock forming minerals. Note that some are less common than others.
The minerals designated as common or very common are most likely to be
present in rocks collected by you or your students from outcrops, stream
beds, back yards, school yards, or gravel pits. Rocks containing
the other minerals are somewhat rare in southern Ontario, but may be found
in areas of northern Ontario. Also note that mineral colour is that
seen on fresh surfaces (weathering of some minerals - especially those
containing iron - produce colours that differ markedly from fresh samples).
| Mineral Streak | Mineral Hardness | Mineral Colour | Specific Gravity | Remarks | Composition | Mineral Name |
| black | 1 to 1.5 | steel grey to black | 2.3 | perfect basal cleavage, may be in hexagonal plates; greasy feel | C | graphite |
| grey-black | 2.5 | grey-black to lead grey | 7.6 | perfect cubic cleavage, crystals commonly cubic; also in granular aggregates | PbS | galena |
| greenish black | 3.5 - 4 | brass yellow often iridescent | 4.1 to 4.3 | as granular aggregates with other Cu minerals, softer than pyrite | CuFeS2 | chalcopyrite
(common in Ontario) |
| red-brown | 5.5 to 6.5 | red-brown to black | 5.3 | fine aggregates or radiating reniform aggregates; occasionally in micaceous aggregates | Fe2O3 | hematite
(common in Ontario) |
| black | 6 | black | 5.2 | usually coarse, or fine granular, no cleavage, strongly magnetic | Fe3O4 | magnetite
(common in Ontario) |
| greenish or brownish black | 6 to 6.5 | pale brassy yellow | 5 | commonly in striated cubic crystals, often tarnishes darker, alters to limonite | FeS2 | pyrite
(common in Ontario) |
| light green to white | 2 to 2.5 | green to grey green | 2.6 to 3.3 | commonly in foliated crystal aggregates, also radiating fans perfect basal cleavage | (Mg,Fe)5(Al,Fe)2Si3O0(OH)8 | chlorite
(very common in Ontario) |
| white to yellow and brown | 3.5 to 4 | red-brown to black | 3.9 to 4.1 | in granular aggregates and malformed crystals. Perfect cleavage in 6 directions | ZnS | sphalerite |
| white | 1.0 | white | 2.7 to 2.8 | in foliated aggregates; perfect basal cleavage, pearly lustre, feels greasy to soapy | Mg3 Si4O10(OH)2 | talc |
| white | 2 | colourless, white, grey | 2.3 | one perfect cleavage, to less distinct cleavages as well, vitreous or pearly, sometimes silky | CaSO4 . 2H2O | gypsum
(common in Ontario) |
| white | 2.5 to 3 | colourless to cream brown | 2.8 to 3.1 | in foliated aggregates, perfect basal cleavage; vitreous to pearly | KAl2Si3O10(OH) | muscovite
(very common in Ontario) |
| white | 2.5 to 3 | sulphur yellow | 2.8 to 3.2 | in foliated aggregates, perfect basal cleavage; vitreous to pearly | K(Mg,Fe)5AlSi3O10(OH)2 | biotite
(very common in Ontario) |
| white | 2.5 | white | 2.2 | in cubic crystals or granular aggregates; perfect cubic cleavage; salty taste | NaCl | halite
(very common in Ontario, but rarely occurs on surface) |
| white | 3 | usually white or colourless | 2.7 | perfect rhombohedral cleavage | CaCO3 | calcite
(very common in Ontario) |
| white | 2 to 5 | green variable | 2.2 | in platy or fibrous aggregates, lustre greasy to silky | Mg3Si2O5(OH)4 | serpentine |
| white | 3.5 to 4 | usually white or colourless or pink | 2.8 | rhombohedral crystals; perfect rhombohedral cleavage; weak reaction to HCl | CaMg(CO3)2 | dolomite
(very common in Ontario) |
| white | 4 | variable, commonly light green | 3.2 | commonly in cubic crystals; perfect cleavage in four directions | CaF2 | fluorite |
| white | 5 | variable, commonly light green | 3.2 | often in hexagonal crystals and granular aggregates, cleavage poor; vitreous to subresinous | Ca5((F,Cl,OH) PO4)3 | apatite |
| white | 5 to 6 | dark green to black | 3.2 | crystals usually elongate, cleavage prismatic at 60o and 120o, vitreous | NaCa2(MgFe)4(AlFe)(SiAl)8 O22(OH,F)2 | hornblende(amphibole)
(very common in Ontario) |
| white | 5 to 6 | dark green to black | 3.2 to 3.4 | crystals usually equant and 8 sided, cleavage prismatic at 90o: vitreous | (Ca,Mg,Fe,Al)2(Al,Si)2O6 | augite(pyroxene)
(common in Ontario) |
| white | 5 to 6 | dark green to black | 3.2 to 3.4 | usually inter-grown aggregates, cleavage prismatic at 90o: vitreous | MgSiO3 | enstatite(pyroxene)
(common in Ontario) |
| white | 6 | pink, grey, white and sometimes green | 2.6 | tabular crystals or coarse aggregates; prismatic cleavage at 90o, vitreous | KAlSi3O8 | orthoclase
(very common in Ontario) |
| white | 6 | white, grey to black, sometimes brown | 2.6 to 2.8 | tabular crystals or coarse aggregates; prismatic cleavage near 90o, vitreous, twinning striations | CaAl2Si2O8 to NaAlSi3O8 | plagioclase
(very common in Ontario) |
| white | 6 to 7 | green | 3.3 to 3.5 | elongate crystals and granular aggregates common; cleavage in two directions - one perfect | Ca,(Al,Fe)3 (SiO4)3OH | epidote |
| white | 7 | usually colourless or white, but quite variable | 2.65 | hexagonal crystals & granular or hypocrystalline aggregates; vitreous, conchoidal | SiO2 | quartz
(very common in Ontario) |
| white | 6.5 to 7.5 | variable, commonly red to purple | 3.5 to 4.3 | Usually equant crystals., also rounded grains and coarse granular aggregates; no cleavage, vitreous to resinous | complex composition of Si, O Ca, Mg, Fe, Mn, Al, Ti, Cr | garnet
(common in Ontario) |
| white | 9 | variable, commonly brown | 4 to 4.1 | in hexagonal columnar crystals or aggregates, lustre adamantine to vitreous, may be dull or waxy when rough, High S.G. | Al2O3 | corundum |
