Aspidosperma spp., Acacia spp., and Schinopsis spp. (see below)
Quebracho is a common name in Spanish used to describe any species of wood that is extremely hard. The name derived from a term meaning "axe-breaker".
This name (often mis-spelled "querbracho" or "querbacho") is, in the USA at least, most often used for "querbracho colorado", but basically because of its highly generic use, the name is a mess. Below is a list of all the botanical name / common name pairs that I have. I do not vouch for the accuracy or completeness of this list, but it does give you some idea what a mess it is. It is, of course, futher complicated by the fact that most, and almost certainly all, of the species listed below have many other common names not shown here and some of those names are more often used for woods that are NOT normally called quebracho (at least in the USA). For example, both Astronium fraxinifolium and Astronium graveolens refer to a wood that is called "goncalo alves" in the USA.
There are at least two groups of "legitimately named" quebracho woods (that is, ones that DO normally use the name quebracho as their common name, or part of their common name, at least in the USA and I believe also in South America). These are the "red" and "white" groups. The red group is primarily Schinopsis lorentzii and Schinopsis balansae, both of the family Anacardiaceae and the white group is primarily Aspidosperma quebracho-blanco of the family Apocynaceae. As you can see, these groups are not even in the same family.
I am currently putting all "quebracho" images on this page because (1) it is not particularly common in the USA and thus is not of primary interest to me, and (2) I don't know enough to properly distinguish them anyway. That's my story, and I sticking with it :-)
my samples: NOTE: these pics were all taken in very bright incandescent lighting ("soft white" at 2700K) colors will vary under other lighting conditions
log end listed as white quebracho (Aspidosperma quebracho-blanco)
planks listed as just "quebracho"
plank listed as quebracho / Schinopsis balansae
plank listed as quebracho blanco / Shinopsis spp.
plank listed as quebracho colorado and speciifically as Schinopsis lorentzii. This same image, somewhat edited but clearly from this original, showed up on two other web site, on one of which it was listed as red quebracho / Schinopsis spp.
plank listed as quebracho colorado
listed as both sides of a thin-wood plank of quebracho colorado. I have no explanation for why it is that the two pics do not look at all like two sides of the same plank, and in fact, I do not believe they are.