Can Miller indices be applied to any crystal found in the field?

Question

If I was to collect a mineral specimen in the field could I visually identify certain faces by using Miller and if so how?

Answer 1

In theory you can,  but you need to be sure to orient the crystal, be able to read the angles, measure the faces, do the arithmetic and carry a list of all the minerals with the miller indices.  Most people find it easier to use the descriptive  tables in mineralogy books.