A comment by Stephen M. Richard about
As an exercise in deciding what lithology terms needed to be defined for our geologic map database here at the AZGS, I worked with Tim Orr here to compile the lithology terms used in a number of published databases. These included the IUGS igneous rock chemistry database (IGBA1), the lithology classification 6 list by Johnson (1999), the lithology words included in the Model 4.3 (Johnson et al. 1999) document, the Petros database, my personal samples database, and USGS DD14 (geochronology) database. We went through the terms (7837, with duplicates removed), edited out the ones that we deemed not useful lithologic names (e.g. alkalic rock, alluvial fan, altered latite-phonolite, 1401 terms all told), and then using the AGI Glossary of Geology (3rd edition) translated abandoned or not recommended usage to recommended usage terms. We ended up with a list of 251 terms. These are 67 lithology terms that appeared 10 times or more, and account for 92% of the usage: LithClass, Count andesite, 463 granite, 311 gabbro, 265 rhyolite, 262 dacite, 241 syenite, 220 diabase, 219 trachyte, 173 granodiorite, 169 tuff, 162 quartz monzonite, 130 phonolite, 114 diorite, 101 monzonite, 90 rhyodacite, 85 quartz diorite, 82 nepheline syenite, 79 trachyandesite, 71 lamprophyre, 69 pumice, 65 cumulate, 57 latite, 55 glass, 53 obsidian, 51 pyroxenite, 48 trachybasalt, 47 basanite, 46 peridotite, 45 norite, 40 nephelinite, 40 aplite, 40 porphyry, 37 granophyre, 37 ash, 31 shonkinite, 29 quartz syenite, 28 tonalite, 28 tephrite, 25 carbonatite, 25 gneiss, 23 mugearite, 23 quartz porphyry, 23 pegmatite, 22 felsite, 22 shoshonite, 21 quartz trachyte, 20 ijolite, 19 schist, 18 dunite, 18 basanitoid, 18 komatiite, 17 theralite, 15 clinopyroxenite, 15 alaskite, 14 pyroclastic rock, 14 anorthosite, 13 agglomerate, 13 absarokite, 12 lherzolite, 11 hawaiite, 11 vitrophyre, 11 essexite, 11 leucitite, 11 ignimbrite, 11 trondhjemite, 10 We have produced a draft lithology classification table that is available for review at http://www.azgs.state.az.us/LithClasses.txt This is a tab-delimited text file; the field names are in the first row. The classification follows the conceptual model put forward in Richard  (http://pubs.usgs.gov/openfile/of99-386/richard.html) Not all of the fields have values yet—null means not entered. This is a work in progress. The table includes 384 lithologic names, culled from the above-described compilation, the AGI Glossary of geology, and the SCAMP word lists (Matti et al ) http://scamp.wr.usgs.gov/scamp/attrib/provpoly.pdf. The definitions are from the AGI glossary. It has not been reviewed in any fashion as yet, but I suggest it might provide a good starting point for definition of lithology names.
Further discussion of Lithology Classification (this page):