There are basically two types of slides, those on glass and the film slides we have today.
While copies can be made of both types of slides, the image quality will not be the same as the original because it is a duplicate.
Glass slides are often confused with glass negatives, but two important differences exist. Also called lantern slides, glass slides, are a positive image and a standard size. The positive image on each lantern slide is sandwiched between two pieces of glass. These slides include a paper mount and taped-sealed edges. Glass negatives come in a variety of sizes and are negative images.
Lantern slides remained popular from 1850 until approximately 1950 and these slides are still used today in many academic disciplines. The introduction of inexpensive film slides in the 1950s replaced them.
Contemporary slides consist of the image and a mount.
There are three types of mounts currently available.
Guidelines for handling slides and for storage can be found in my book. Or, feel free to email me.