An afghanite is a hydrous hexagonal feldspathoid mineral of the cancrinite group.

The lavas erupted from mid-oceanic ridges are called basalts. This lava contains quarts, feldspathoid, and plagioclase. Basalts has gray to black color.

The lavas erupted from mid-oceanic ridges are called basalts. This lava contains quarts, feldspathoid, and plagioclase. Basalts has gray to black color.

Basalt is a commonly extrusive volcanic rock. It is usually grey to black and fine-grained due to rapid cooling of lava at the surface of a planet. Unweathered basalt is black or grey. Basalt is defined as an igneous rock that contains less than 20% quartz and less than 10% feldspathoid and where at least 65% of the feldspar is in the form of plagioclase. On Earth, most basalt magmas have formed by decompression melting of the mantle. Basalt has also formed on Earth's Moon, Mars, Venus, and even on the asteroid Vesta. Basalt is being forming all the time from volcanic eruptions and activity.

The first thing one would look at is if there are minerals present that are large enough to either be identified with the naked eye or with a handlense. Most lavas have large volumes of extremely finegrained material or glass whereas plutonic rocks that mostly crystallize in depths of several kilometers are usually composed of millimeter sized minerals. Further differentiation of ejecta can be done like (ash, lapilli, volcanic bombs, pahoehoe-lava etc.).

One can then look at the mineralogical composition of these rocks to define whether they are basic (little silicon) like basalts/gabbros or acid (a lot of silicon) like rhyolites/granites. The usual classification is the QAPF-diagram (quarz, alkali feldspar, plagioclase, feldspathoid), which is composed of two ternary diagrams. If quarz is present the ternary diagram including quarz is used, otherwise the one with an feldspathoid endmember is chosen for classification.

This field description is then usually followed by a series of lab analyses of the chemical and isotopic composition of the rock in order to be classified via their elemental composition. One example is the TAS-diagram (total alkali elements versus silicon dioxide content).