The plagioclase feldspars are a solid solution series. The end stones are albite and anorthite. Intermediate specimens include labradorite, a well known gem when it's chatoyant, and bytownite, found in Minnesota.
The feldspathoid group are framework silicates containing less sillica than the feldspars. These were formed in silica-poor areas and therefore are not found in areas where there is a lot of quartz. Sodalite belongs to this group.
Two other related groups are scapolite, which in its yellow form has been used as a gem, and the zeolite group which includes 22 well defined species. The zeolite group includes stilbite, chabazite and heulandite, all of which form into beautiful crystals.