Glen Avon Quarry (Glen Avon Limestone deposit; Mathews), Glen Avon, Riverside Co., California, USA
|Latitude & Longitude (WGS84):||34° 1' 26'' North , 117° 29' 3'' West|
|Latitude & Longitude (decimal):||34.0238888889, -117.484444444|
A former marble (dimension) deposit/quarry located in the SE¼NW¼SW¼ sec. 2, T2S, R6W, SBM. MRDS database stated accuracy for this location is 100 meters.
Local rocks include pre-Cenozoic metasedimentary and metavolcanic rocks undivided.
Workings include unspecified surface openings.
The first and southernmost quarry, also the smallest, is totally in recrystallized limestone. In the coarser parts where the calcite rhombs get up to about an inch across there are regions containing nice micros of golden brown phlogopite. In the finer grained dark appearing calcite there are regions with nice graphite micros. A couple of small regions near the entrance on the right contain fine grained purple spinel and chondrodite. I found one axinite crystal in weathered material on the left. A pit below this quarry contains veins of fibrous tremolite.
The walls of the two larger quarries are largely calc-silicate rock and I spent the bulk of my time with that. Below the middle quarry I broke up a rock that contained numerous cinnamon brown garnets to about half and inch, but mostly smaller.
In the northern quarry I worked and area of the north wall that appeared to be a very dirty porous plagioclase and brought home several chunks. They required a lot of cleaning and trimming, but proved to be quite interesting. It appears that at one time this rock was an intergrowth of diopside and plagioclase with minor titanite and zircon. It appears that as the temperature dropped in the fluid rich environment diopside became unstable and was largely leached out. Later still actinolite, axinite, and apatite were deposited in the resulting cavities. After much cleaning I recovered nice micros of all the minerals mentioned from these pieces. The axinites are especially well developed.
Even though we worked in slow motion because of the heat I think everybody found something of interest. About 5:30 though we all decided we had had all the fun we could stand for one day and retired to a nearby Mexican restaurant recommended by Anne for food and refreshment and conversation. Now I am ready to go back to Glen Avon and try it again soon.
6 valid minerals.
Rock Types Recorded
Select Rock List TypeAlphabetical List Tree Diagram
This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.
Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org
|Pleistocene - Middle Pleistocene|
0.0117 - 0.781 Ma
|Old alluvial-fan deposits, Unit 1|
Age: Pleistocene (0.0117 - 0.781 Ma)
Description: On south side of San Bernardino Mountains, moderately dissected interstratified sand and gravel capped by soils having Bt horizons as much as 50 to 150 cm thick (Ramona soils of Woodruff and Brock, 1980). On north side of San Bernardino Mountains, reddish-brown alluvial fan deposits of primarily sand- to boulder- sized clasts that are moderately consolidated and slightly to moderately dissected. Distinguished as terraces cut into locally older Qof sediments. On north side of San Bernardino Mountains, chiefly restricted to small area northeast of Silverwood Lake. There, distinguished from other Quaternary units using aerial photographs; deposits are distinctly elevated and more dissected than Qyf units, but less dissected than locally older Qof units
Reference: Morton, D.M., F.K. Miller . Geologic Map of the San Bernardino and Santa Ana 30' x 60' quadrangles, California. U.S. Geological Survey Open-File Report 2006-1217. 
|Cretaceous - Paleoproterozoic|
66 - 2500 Ma
|pre-Cenozoic metasedimentary and metavolcanic rocks undivided|
Age: to Cretaceous (66 - 2500 Ma)
Stratigraphic Name: Kings Sequence; McCoy Mountains Formation (part); Palm Canyon Complex; Placerita Formation
Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052. 
Housley, Robert (2001), Microbits (Southern California Micromineralogists bulletin) (Oct/Nov).
USGS (2005), Mineral Resources Data System (MRDS): U.S. Geological Survey, Reston, Virginia, loc. file ID #10077142 & 10115667.
U.S. Bureau of Mines Minerals Availability System/Mineral Industry Location System (MAS/MILS): file #0060650826.