Currently the most popular, granite came into widespread use by 1900 , although there are some reported uses as early as 1870.
It is a hard stone that requires a great deal of skill to carve. These days a rubber stencil is used for the names, dates and emblems which are then sandblasted onto the stone’s surface. 
Granite has also been used to replace some of the more weathered sandstone and marble markers in older cemeteries.
This red granite marker (above), placed in 1932, marks the 1852 and 1857 deaths of my fourth great-grandparents and their arrival in Canada in 1833.
Aside from the isolated return of these exclusive monuments, some modern-day memorials do not use stone at all, but involve planting trees.  These living memorial tree programmes exist in Red Deer, Lacombe, Wainwright, Calgary, High River and Sylvan Lake to name a few locations in Alberta.
Cross-vaulted obelisks are four-sided markers with arch-like points that cross over to the adjoining sides. This approach is a variation of the column-standard obelisk originated by the Egyptians.
These four-sided gravestones began appearing in 1850 and are still in use today. They continue to be mistakenly referred to as masonic-style stones.
In this red granite example (below), eleven burials from 1852 to 1997 are recorded with ample room for more to be added later.
 John Walters, the Graveyard Groomer [Internet] http://www.graveyardgroomer.com/Articles.htm
 Granite engraving at Lons Memorials (Belleville, ON) [Internet] http://www.lonsmemorials.com/monunltr.htm
 “How to Date a Tombstone,” Genealogy Trails [Internet] http://genealogytrails.com/main/readingheadstones.html
 “Memorial Tree Program,” Town of High River, Alberta, Canada [Internet] http://www.highriver.ca/town-hall/departments/community-services/parks-a-rec/memorial-legacies
 Stones of Faith [Internet] http://www.pagstones.com/pgs_symbols_general.page.shtml
 Escape to the Silent Cities [Internet] http://escapetothesilentcities.blogspot.com/2010/09/sunday-styles-vaulted-obelisks.html
 The Anatomy of Tombstones [Internet] http://www.colorado-cemeteries.com/tombstones.html