Rock with sparkly layer

[tonocats]

So I have several of these large rocks that have the appearance of a 1/4” or so, layer that looks almost like it melted on the rock. One rock is 14” tall and the others are of varying smaller sizes. This layer is extremely hard but I was able to wedge a chisel in and knocked off a small piece of it. The layer looks gray in color but underneath it appears more white in color. It sparkles when in the sun. These rocks were unearthed from a hillside in San Dimas, CA where heavy machinery was clearing an area for construction. This was more than 40 years ago and in the time since then nobody has been able to tell me what this stuff is. I don’t know what type of rock it is but it’s not extremely hard. The layer of stuff on it is harder than the rock itself. The layer almost looks like it contains crystals. Would be grateful to anyone who can identify what this is.

 

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[Plug N Play]

Druzy

 

[A2coins]

Welcome to tent you can post on the rock and gem forum for more opinions

 

[Reanm8er]

Welcome tonocats! I had to look it up but I think plugnplay is right! Great job.