Tridymite (high temp Quartz Paramorph) & Amethystine Quartz – Location: Thomas Range, Juab Co., Utah. Miniature (see photo for more details). Here we have a nice specimen of the quartz paramorph (same formula but higher temperature form that is a distinct species) tridymite. This specimen is from a relatively new discovery that was made by us (topazminer) in the Thomas Range, Juab Co., Utah. It formed in a high temperature fumarolic vent in rhyolite. The walls of the vent are lined with small but sharply formed amethystine quartz with the tridymite, along with cristobalite, formed on the surface of the vent walls. Normally tridymite forms as very small microscopic crystals; however, these crystals are easily visible. The crystals are a very light pale bluish to bluish-grey color and form clustered rosette Trilling groups (twinning). Tridymite is a high temperature species of SiO2 that is often associated with and mixed with another high temperature quartz paramorph cristobalite. Larger tridymite crystal specimens are practically non-existent (with rare exceptions). There is also some small but sharply formed gemmy light pale purplish colored amethystine quartz crystals.