The following article lists the characteristics of an activity that makes it Montessori.
A Montessori method is an educational approach characterised by learner choice, an enriching environment and educators who facilitate the learner’s natural bent for learning. It was devised during the 1900s by Dr Maria Montessori, a physician, anthropologist and pedagogue over a professional career that spanned over fifty years.
For more information, please read the following: Activities In A Montessori Classroom