# Rock or possible fossil identification needed

Found in Cressy River, Stanislaus County, California in April 2014.

The rock is 3" $\times$ 1" weight is 7 oz and from 1-10 on hardness i give it a 8 . I found it in the river. It caught my eye because 98% of the rocks there are oval and smooth. It has slightly magnetic properties.

• What's "7-density"? – Gimelist Oct 13 '15 at 11:31
• It is hard to tell from the image, is the rock gray or does it have a metallic luster? – Gary Kindel Oct 13 '15 at 12:49
• I agree with Gary, it's impossible to tell without much more detail. – Gordon Stanger Oct 13 '15 at 13:09
• Hardness 8: does that mean that you can't scratch it with quartz? – Gimelist Oct 13 '15 at 20:56
• To OP and everyone asking for details, please read this guide. – naught101 Oct 14 '15 at 2:40

Looks like a lodestone a naturally magnetic mineral. Look up magnetites and lodestones. Hope this gives you a good start on where to search.

Based on the dimensions you provided and the photograph, the density is likely between 5 and 9 g/cm3, assuming cylindrical volume with height between 2.8-3 inches and radius between 0.4-0.5 inches. Based on this density and the weak magnetic properties, you have an iron-rich rock. Most fossils are comprised of calcite or a mineral with a similar density of around 3 g/cm3, with the exception of cases where metallic minerals replace the original material.

The location provided is useful. However, I could not find a Cressy River, and I assume you are referring to the Merced River. This area flanks mountains that are rich in gold placer deposits and associated minerals, including iron. It is most probable that you found a iron-bearing mineral associated with the igneous or metamorphic rocks in the mountains.

Based on these meteorite classifications I would think it is a meteorite. Some classifications that you mention line up with those found in the site I linked to, such as:

• Magnetism - Practically all meteorites contain a significant amount of extraterrestrial iron and nickel, so the first step in identifying a possible meteorite is the magnet test.
• Weight and Density - You said in the question that it weighs 7 oz. According to the link above, a meteorite is normally heavier than normal rocks. I don't know if your rock meets this qualification, for I have not held it myself. You will have to judge that.
• Fusion CrustWhen a meteoroid (a potential meteorite) streaks through our atmosphere, tremendous heat is generated by atmospheric pressure. The surface of the rock melts and the air around it incandesces. As a result of this brief but intense heating, the surface burns and forms a thin, dark rind called fusion crust. It would appear that your rock could possibly have gone through this process.
• Regmaglypts - Regmaglypts, popularly known as thumbprints, are oval depressions-often about the size of a peanut-found on the surface of many meteorites. These indentations look much like the marks a sculptor might make with his fingers on a wet lump of clay, hence their name. Regmaglypts are created as the meteorite's outer layer melts during flight and they are another feature unique to meteorites. I do not know if you have noticed this on your rock, but from the pictures I can't seem to find any.
• Flow Lines - As our typical meteorite burns through the atmosphere, its surface may melt and flow in tiny rivulets known as flow lines. These patterns formed by flow lines can be minute, often thinner than a strand of human hair, and they are one of the most unique and intriguing surface characteristics of meteorites. It would appear as if your rock has these lines.

To find out what it is exactly, you could take it to a lab to be tested. There you can get a good scientific answer.

• The prior probability of a random specimen being a meteorite is very low, so the evidence for a positive identification needs to be very compelling. To put it another way: 'meteorite' should probably never be a 'first guess'. – kwinkunks Nov 23 '15 at 19:34
• It is my first guess, but it may not be others first guess. It is what I believe it is from the pictures. It has been more than a month now since The Void asked this question. – A Child of God Nov 23 '15 at 23:06
• @kwinkunks Do you have a better idea? – A Child of God Nov 23 '15 at 23:06
• @Kwinkunks-My thoughts now suspect a possibly fossil of some type.What are your thoughts on my new assumption?I know you cant give a correct explanation due to only having a visual and lack of data provided,I really respect the knowledge and info you give even with certain circumstances. – user5434678 Nov 26 '15 at 9:17
• @kwinkunks: Agreed. Or else one would think that the entire Big Island of Hawaii fell out of the sky based on the hand samples found there. – Knob Scratcher Feb 6 '17 at 15:22