Every crystal manufacturer has their own unique process and set of materials for making crystal. In the past crystal manufacturers would add lead to the crystal to increase clarity and refraction. The higher amount of lead, the higher the quality of crystal. A high quality crystal would have over 30% lead content and a medium quality crystal would have 20% to 30% lead. In recent years manufacturers have researched crystal production to create a lead free crystal that has that has appearance of the leaded crystal. Today most quality crystals still have the high clarity and refraction, but are now lead free.
Austrain crystal has long been know for its high quality, high clarity, high refraction, and high polish. A quality crystal will have a high polish on all of the crystal surfaces giving it a glossy shine. Many lower quality crystals will polish the facet surfaces, but not the crystal edges. A quality manufacturer will be able to produce uniform crystals that are reliable in shape, weight, and finish. A low quality crystal will provide a refraction effect that is only slightly better than glass.
Some manufacturers, like Swarovski, will laser etch their crystals to provide a reliable identifying feature for the customer. Other ways to identify crystals are facet patterns and weight. A higher quality crystal will weigh more than a lower quality crystal, due to metal and mineral content. Each manufacturer tends to create their own specific facet design depending on the quality and desired effect. A Swarovski Strass crystal octagon will have more facets than a Swarovski Spectra crystal octagon or an Asfour crystal octagon. If you question your crystal quality, an internet search may not always tell you what brand it is, but it may be able to tell which brands it isn't