Image credit: Scott Brande
Identification is the action of assigning a name to an object. Identifying an unknown metamorphic rock requires the observation of its features and the matching of those features to named categories of rocks in a classification.
The identification process is illustrated by the diagram below centered on an unknown sample.
To identify a metamorphic rock by name using the simplified classification, we must be able to recognize particular features of metamorphic rocks.
In this simplified treatment, characteristics will be restricted to those typically observable with the naked eye and with a few simple tools, e.g., dilute, cold, HCl (hydrochloric acid), a glass plate.
More advanced students will need to seek an alternative resource for this topic.
In the simplified classification above, three features in combination lead to the name of common metamorphic rocks.
Click links below for details on each feature.
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Foliation is recognized by an alignment of material.
Image credit: Scott Brande
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Calcite mineralogy is recognized by a vigorous reaction to cold, dilute HCl. The acid test distinguishes marble from all other metamorphic rock
Image credit: Scott Brande
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Grain size is assessed without magnification aids. Particles range from microscopic to boulder-sized blocks.
Image credit: Scott Brande