Utilizando los datos quakes:

library(datasets)
head(quakes)
##      lat   long depth mag stations
## 1 -20.42 181.62   562 4.8       41
## 2 -20.62 181.03   650 4.2       15
## 3 -26.00 184.10    42 5.4       43
## 4 -17.97 181.66   626 4.1       19
## 5 -20.42 181.96   649 4.0       11
## 6 -19.68 184.31   195 4.0       12
library(leaflet)
leaflet() %>% 
  addTiles() %>% 
  addMarkers(lng = quakes$long,
             lat = quakes$lat,
             clusterOptions = markerClusterOptions())
quakes$Class<-cut(quakes$mag, breaks=c(0,4,5,6,7,10))

pal <- colorFactor(palette = c("red", "blue", "#9b4a11", "darkgreen", "magenta"),
levels = c("(0,4]", "(4,5]", "(5,6]", "(6,7]", "(7,8]"))


quakes%>%
leaflet() %>% 
  addTiles() %>% 
  
addCircleMarkers(lng = quakes$long, lat = quakes$lat, radius = 1,
                   color = ~pal(Class)) %>% 
  addLegend(position = "bottomright",
            pal = pal, 
            values = c("(0,4]", "(4,5]", "(5,6]", "(6,7]", "(7,8]"))