Rare Tridymite Crystals (high temp Quartz Paramorph) – Location: Thomas Range Juab Co. Utah. Miniature (see photo for more details). Here we have a rare specimen of crystals 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. Normally tridymite forms as very small microscopic crystals; however these crystals are much larger and easily visible. 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 very rare except for this rare and unusual deposit.