Quarterly Crystal: Panasqueira Quartz
With its relatively high hardness and high degree of transparency, colorless rock crystal quartz is the perfect host for an abundance of fluid and mineral inclusions. As a common crustal mineral, it sometimes forms as solid single crystals and crystal clusters.
This issue’s Quarterly Crystal, a 751.95 ct double crystal measuring 110.54 × 50.30 × 24.82 mm from Minas da Panasqueira in Portugal (figure 1), comes from the personal collection of Jordi Fabre of Fabre Minerals in Barcelona. Examination of the two parallel quartz crystals revealed numerous colorless to green, transparent to translucent euhedral inclusions, identified by Raman analysis as fluorapatite (figure 2). Some of these fluorapatite inclusions surrounded a much larger dark brownish orange protruding crystal confirmed as cassiterite (figure 3).
The colorless to green fluorapatite crystals show directional deposition and are along a phantom plane, situated only on one side of the quartz specimen. This suggests that they are syngenetic with the quartz host.
Quartz is relatively common at the Panasqueira mine. This “floater” quartz crystal group, which is recrystallized at its base, is an excellent host for the numerous inclusions of fluorapatite and the solitary cassiterite crystal.
