Successively described and analyzed by many specialists since 1851, its a mixture of feldspar, hornblende, biotite (black mica) and quartz.
It is considered an intrusive rock with a texture similar to “granite”, the term “granite” designating a hard stone used in civil engineering. The matrix is coarser than those of hornblende granite, of anorthite and of bytownite cashing veins, specially the pebbles areas (not “orbits”), greenish-blue to blue-gray, with a density of about 2.80.
Some spheroidal clusters, only feldspathic or some mosaics of very fine misguided anorthite debris, of varying sizes, isolated or clustered and unevenly distributed, form some alternating concentric light and dark areas whose genesis is not exactly explained.
The diameter of these pebbles is 2 to 30 centimeters and the number of sheets from the unit to twenty, their spacing being along a geometric progression.