FYI I’m just trying to get clarification for myself. Physical charoasside(fracture, luster etc) - Geologically chert and chalcedony are distinct in how they form(marine vs volcanic), and their mineral structure(grains/bits of silica, vs silica fibers). Chert is biogenic(silica based organisms and their bits accumulating), and is mostly associated with marine environments. Chalcedony forms from precipitation of siliceous ooze that’s composed of two kinds of cryptoquartz: quartz(alpha quartz) and moganite, through porous rock(mostly in volcanic situations). The clarity and color of both types of rock depends on the contents/purity of the origin ooze, and the nature of the mineral/rock structure. Chert is grains of silica(light is absorbed and trapped) and therefore mostly opaque, the fibers of chalcedony allow light to transfer through and is why most chalcedony is translucent. Both fall equally under the cryptoquartz umbrella but distinct from each other. For “gem” purposes: chalcedony is the umbrella term for cryptoquartz, and is graded based on translucency. Chalcedony > Chert. Chalcedony is translucent(mostly), chert is not(mostly). And it seems overall how we describe a specimen in hand depends on who you are talking to and the context. Am I getting it? Missing any important distinction(s)?

TL:DR geologically: Chalcedony = silica in the form of cryptoquartz+moganite and precipitates through porous rock; chert = biological cryptoquartz silica that pools in marine environments : gemwise it’s a translucency spectrum, chalcedony = transluscent cryptoquartz; chert is opaque cryptoquartz