December 31, 2016

31 Days of Utah Rocks

We’ll start with Coal – Utah’s State Rock

The fossilized remains of plants, coal usually occurs in layered, sedimentary deposits.  It is brown or black and made up of an irregular mixture of chemical compounds called macerals, which are analogous to minerals in inorganic rocks.  Unlike minerals, macerals have no fixed chemical composition and no definite crystalline.

Different varieties of coal are formed depending on the kinds of plant material, varying degrees of conversion and the presence of impurities.  Four varieties are recognized.

Lignite s the lowest grade and is the softest and least coalified variety. It forms from peat under moderate pressure.

Sub-bituminous coal is dark brown to black.


Bituminous coal is the most abundant and is commonly burned for heat generation.

Anthracite is the highest grade and the most highly metamorphosed foam of coal.  It contains the highest percentage of low-emission carbon and would be an ideal fuel if it were not relatively scarce.

Utah’s coal deposits are Bituminous and are not usable for jewelry.  It formed from plant material living in marshes or swamps along coastal areas of inland seas that filled central Utah during the Cretaceous period.  These swamps, similar to today’s swamps of the south, took millions of years to alter from swamp sediment to coal.  It takes 10 feet of accumulated plant material to form one foot of coal.

We’ll spend the next 30 days exploring the many deposits of rock in Utah.  What they are and where you could find them.  I hope you’ll join me.