There are a variety of Birthstone Charts as you may have already discovered! There are different charts by era (traditional v modern), by country (eg. Polish, Italian), by culture (eg. Arabic, Hebrew), or by Zodiac sign (eg. astrological, planetary). Some birthstone charts have more than one gemstone per month or list secondary or alternative gemstones. I have also found that the same chart type, for example a Traditional Birthstone Chart, can differ from source to source.
The charts below are designed by Monthly Birthstones and are free for your own personal use. They are high resolution A4 pdf documents suitable for printing..
Modern Birthstone Chart
The Modern Birthstone Chart has one gemstone per month and is the most popular version.
Official Birthstone Chart
The Official Birthstone Chart for the USA was declared in 1912 with subsequent amendments in 1952 and 2002. In June 2016 Spinel was added as a new August birthstone (Ref: American Gem Trade Association).