GCBJCYX They Passed This Way (Earthcache) in California, United States created by Chet13

GCBJCYX ▼

A cache by Chet13 Message this owner

Hidden : 2/7/2026

Difficulty:

Terrain:

Size: Size: other (other)

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Geocache Description:

Welcome to Old Town Temecula

In Old Town Temecula, the massive granite monument They Passed This Way preserves both human history and a far older geologic story. The towering stone and its base blocks are made of granite that formed deep underground millions of years ago. The stone was left largely in its natural state, allowing its texture, crystal structure, and early signs of surface alteration to remain visible. This EarthCache invites you to examine mineral composition, crystal size, and natural weathering patterns recorded within the granite.

The Story of Granite

Granite is an igneous rock that forms when molten rock, called magma, cools slowly deep beneath Earth’s surface. Because the cooling occurs over millions of years underground, minerals have time to grow into large, visible crystals. Early-forming minerals, like feldspar, often grow larger and blockier, while later-forming minerals, like quartz and mica, fill in the remaining spaces. Once formed, the granite remained buried until tectonic forces pushed it upward and erosion removed overlying rock layers. The granite used for this monument was quarried from the long-abandoned Ed Querry Ranch quarry in the hills south of Temecula. Some of the granite blocks had been cut decades earlier for construction projects, while the large central boulder was selected from naturally shaped stone at the quarry. The monument’s stone remains mostly unpolished, preserving its natural textures and visible mineral grains. Granite is very durable because its interlocking crystals make it resistant to breaking, but it slowly changes over time through natural processes at the surface. Cracks can form from repeated heating and cooling, mineral grains can loosen, and chemical reactions with water and air can gradually alter the appearance of feldspars and other minerals. Over long periods, these processes slowly reshape the rock and reveal the history of its exposure at the Earth’s surface.

Typical Granite Composition

Granite is typically made up of several common minerals that crystallized as magma cooled slowly beneath Earth’s surface. Each mineral contributes to the rock’s overall appearance, color, and strength.

Quartz - Quartz is usually clear, milky, or light gray and has a glassy shine. It is very hard and resistant to weathering. In granite, quartz helps give the rock its durability and can often be seen as irregular, slightly translucent grains.
Potassium Feldspar - Potassium feldspar commonly appears pink, white, or light gray. It forms large, blocky crystals and is often one of the most visible minerals in granite. This mineral contributes to the light colored background seen in many granites.
Plagioclase Feldspar - Plagioclase feldspar is typically white to gray and can sometimes show faint lines or striations on crystal surfaces. It forms rectangular shaped crystals and makes up a significant portion of most granites.
Biotite - Biotite is a dark mica mineral that forms thin, shiny flakes. It is usually black or dark brown and is one of the main minerals responsible for darker colors in granite. Higher amounts of biotite can cause granite to appear much darker overall.
Amphibole - Amphibole minerals, such as hornblende, are dark green to black and form elongated or needle like crystals. Like biotite, amphibole absorbs more light and contributes to the darker appearance of some granites.

Tasks for This EarthCache

To log this EarthCache, visit the site and complete the following tasks. Send me your answers via Geocaching or email.

Include “They Passed This Way - GCBJCYX” on the first line of your message.
Observe the monument and describe the colors and textures of the stone. How do these features reflect that the rock is natural granite?
Describe the overall crystal size. Are the mineral grains large and easy to see or very small? What does this indicate about how fast the magma cooled underground?
Identify at least two different minerals visible in the granite. Describe their features and explain how you recognized them. Which mineral appears to be the most abundant?
Examine the surface of the granite for signs of weathering and describe what you observe. Which processes are likely responsible?
In your log, attach a photo of yourself or a personal belonging with the monument in the background. (Note: photos predating the publication of this EarthCache are not accepted.)