1 Definition
1.1 Definition
Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers called coal beds
Scoria is a dark-colored extrusive igneous rock with abundant round bubble-like cavities
1.2 History
1.2.1 Origin
1.2.2 Discoverer
John Peter Salley
Unknown
1.3 Etymology
From the Old English term col, which has meant mineral of fossilized carbon since the 13th century
From late Middle English (denoting slag from molten metal), from Greek skōria refuse, from skōr dung
1.4 Class
Sedimentary Rocks
Igneous Rocks
1.4.1 Sub-Class
Durable Rock, Soft Rock
Durable Rock, Medium Hardness Rock
1.5 Family
1.5.1 Group
1.6 Other Categories
Coarse Grained Rock, Fine Grained Rock, Medium Grained Rock, Opaque Rock
Fine Grained Rock, Opaque Rock