Also known as the Petrick (peet-rick) Quarry, this site was quarried for the Rapakivi granite used in the construction of several state office buildings in Austin, 80 miles to the east. The site ceased operation in early 1942. A very prominent rare-earth pegmatite bisects the granite dome from southwest to northeast and is the source of the unique rare-earth minerals found here. The mineralization of Petrick closely resembles that of its more famous cousin, the Baringer Hill Pegmatite, 2 miles to the north, 90 feet beneath the waters of Lake Buchanan.
The minerals found here are almost too numerous to list separately.
Cross section of a pegmatite boulder that was found to contain a pod of radioactive yttrialite in the form of an asterism, or star shaped fracture pattern. (right of center).
The dark violet inclusions above the asterism are the "puce" variety of chlorophane fluorite initially discovered two miles to the north, at Baringer Hill, by William Hidden in 1905. This fluorite was found to glow softly in the dark at room temperature with no external excitation.
I am pointing to a 1x3x6 cm crystal of radioactive gadolinite, sandwiched between two plates of black biotite mica.
Petrick quartz/hyalite under SW UV
Petrick sanidine, AKA moonstone. When held at just the right angle in sunlight, a brilliant blue flash, or schiller, becomes visible. When cut as a cabachon, the schiller displays a blue "cat's eye" effect.
This beautiful 4 cm x 1 cm radial foliated book of molybdenite on pink microcline was collected from Petrick in March of 2006.