Hardness

Soft – can be scratched by a fingernail, Mohs’ 1-2; Medium – can be scratched by a knife or nail, Mohs’ 3-5; Hard – cannot be scratched by a knife but can scratch glass, Mohs’ 6-9; Diamond is the hardest known mineral, Mohs’ 10.

Galena

A metallic luster means shiny like polished metal. For example cleaned polished pieces of chrome, steel, titanium, copper, and brass all exhibit metallic luster as do many other minerals. Of the nonmetallic lusters, glassy is the most common and means the surface of the mineral reflects light like glass.

Minerals with metallic luster look shiny like metals. Gold, silver, and copper have metallic luster. Minerals with non-metallic luster can be divided into groups of minerals with earthy, waxy, vitreous (glassy), adamantine (diamond-like), resinous (like resin), pearly, silky, or dull luster.

Shale is a very fine-grained rock (the individual grains are too small to see with your naked eye) that contains a lot of organic material (decayed plant and animal remains, poop, algae, bacteria) that gives the rock its characteristic dark grey/black color.

Sedimentary rocks are called secondary, because they are often the result of the accumulation of small pieces broken off of pre-existing rocks. There are three main types of sedimentary rocks: Clastic: your basic sedimentary rock.

Rocks composed of particles derived from the erosion or weathering of preexisting rocks, such as residual, chemical, or organic rocks formed of detrital, precipitated, or organically accumulated materials; specif., clastic sedimentary rocks.

The most common secondary minerals are as follows: 1. The kaolinite created by the processes of change and chemical weathering of feldspar….5.2 Classification of igneous rocks.