BH250-178
Title
BH250-178
Subject
Zabriskie Silica-cemented Sandstone (Quartzite)
Description
Major Mineral: quartz
Minor Mineral: silica overgrowth
The Zabriskie Quartzite is a well-known Lower Cambrian rock unit exposed prominently in Death Valley National Park, particularly around Emigrant Pass and in nearby ranges such as the Funeral Mountains. Although mapped as a quartzite, some geologist argue that it is actually a silica-cemented sandstone, as evidenced by the presence of silica overgrowth cement visible in thin section.
Both quartz grains and silica-overgrowth that surround the quartz grains, exhibit similar optical properties under crossed polarized light (XP)L, making them difficult to distinguish in polarized light. However, under plane polarized light (PPL), the quartz crystals show slightly higher relief compared to the silica overgrowth. This suggests that the overgrowth is amorphous or microcrystalline, differentiating it from the crystalline quartz grains.
In BH250-178, many large quartz grains are cut perpendicular to the c-axis, producing beautiful optic axis interference figures under the microscope. This thin section is excellent for teaching about quartz’s low birefringence, its interference colors, and how to determine the orientation of the c-axis using a mica plate (accessory plate). It is also ideal for demonstrating length-fast and length-slow behaviors in minerals.
Rock Type: There are two units that were sample from this sandstone, lower unite (BH250-178b) and an upper unit (BH250-178). Both are predominantly silica-cemented sandstone (often called quartzite), with interbedded quartz sandstone, siltstone, and minor shale. The upper unit is dark colored rock. The lower unit is typically light gray to pinkish, sometimes buff-colored, with sugary, fine- to medium-grained, composed of very mature quartz grains; well-cemented and highly resistant to weathering. Sedimentary structures include features such as cross-bedding and ripple marks.
There are many sandstones that correlate lithologically and also in age with the Zabriskie sandstone. The Zabriskie Quartzite correlates with several other Lower Cambrian quartzite or sandstone formations across the western and southwestern USA, all deposited along the Cordilleran passive margin of Laurentia. These formations include, Tintic Quartzite (Utah), Tapeats Sandstone (Arizona), Zabriskie Quartzite itself (California)
Additionally, the Zabriskie Quartzite is age-correlative, though not a direct lithologic equivalent, with the Mount Simon Sandstone of Wisconsin and Minnesota, representing the same broad Cambrian marine transgression across the North American craton.
Minor Mineral: silica overgrowth
The Zabriskie Quartzite is a well-known Lower Cambrian rock unit exposed prominently in Death Valley National Park, particularly around Emigrant Pass and in nearby ranges such as the Funeral Mountains. Although mapped as a quartzite, some geologist argue that it is actually a silica-cemented sandstone, as evidenced by the presence of silica overgrowth cement visible in thin section.
Both quartz grains and silica-overgrowth that surround the quartz grains, exhibit similar optical properties under crossed polarized light (XP)L, making them difficult to distinguish in polarized light. However, under plane polarized light (PPL), the quartz crystals show slightly higher relief compared to the silica overgrowth. This suggests that the overgrowth is amorphous or microcrystalline, differentiating it from the crystalline quartz grains.
In BH250-178, many large quartz grains are cut perpendicular to the c-axis, producing beautiful optic axis interference figures under the microscope. This thin section is excellent for teaching about quartz’s low birefringence, its interference colors, and how to determine the orientation of the c-axis using a mica plate (accessory plate). It is also ideal for demonstrating length-fast and length-slow behaviors in minerals.
Rock Type: There are two units that were sample from this sandstone, lower unite (BH250-178b) and an upper unit (BH250-178). Both are predominantly silica-cemented sandstone (often called quartzite), with interbedded quartz sandstone, siltstone, and minor shale. The upper unit is dark colored rock. The lower unit is typically light gray to pinkish, sometimes buff-colored, with sugary, fine- to medium-grained, composed of very mature quartz grains; well-cemented and highly resistant to weathering. Sedimentary structures include features such as cross-bedding and ripple marks.
There are many sandstones that correlate lithologically and also in age with the Zabriskie sandstone. The Zabriskie Quartzite correlates with several other Lower Cambrian quartzite or sandstone formations across the western and southwestern USA, all deposited along the Cordilleran passive margin of Laurentia. These formations include, Tintic Quartzite (Utah), Tapeats Sandstone (Arizona), Zabriskie Quartzite itself (California)
Additionally, the Zabriskie Quartzite is age-correlative, though not a direct lithologic equivalent, with the Mount Simon Sandstone of Wisconsin and Minnesota, representing the same broad Cambrian marine transgression across the North American craton.
Coverage
Location: Death Valley, California, USA
Nearby Geographic Figure: Death Valley
GPS Coordinates: 35.891239, -116.0763
Nearby Geographic Figure: Death Valley
GPS Coordinates: 35.891239, -116.0763
Creator
Bereket Haileab
Source
From the rock collection of Bereket Haileab. Sample BH250-178. Housed at Carleton College in Minnesota.
Type
Thin section and hand sample
Relation
Collection
Citation
Bereket Haileab, “BH250-178,” BH250 Mineralogy Teaching Collection, accessed April 26, 2026, https://bereket-haileab.geology.sites.carleton.edu/items/show/241.