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Geode Breakdown!

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Geodes are so fun to crack open because they can reveal a surprise inside. Not all geodes are created equal. Ideally, a perfect geode opens up to a crystal encrusted interior with a hollowed out center, but many only have solid rock on the inside and you can’t see the crystal formations. The purpose of this project is to see if you randomly get the encrusted crystal interior or if by taking certain measurements first, like mass, volume and circumference, can show a connection between a perfect inside or a geode dud.

PURPOSE

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Hypothesis

If the geode has a high density, then the interior of the geode will be a solid rock with no crystals.

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AMOUNT	ITEMS
70	Geodes
20 cm	Piece of string
1	Ruler
1	Scale
1	250 mL graduated cylinder
200 mL	Water
1	Hammer
1	Chisel

MATERIALS

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PROCEDURE

With a marker, label the geodes 1-70.
Measure the circumference in cm of the goede with the string by wrapping the string around the visually widest part of the geode.
Find the mass in grams of the goede with the scale.
Measure the volume in mL with the graduated cylinder by using the water displacement method.
Calculate the density using the formula of mass divided by volume.
Record all data
Crack open the geodes with the hammer and chisel.
Make observations about their internal crystal structure. Record if the geode has crystals, sandy interior or solid rock matter.

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GEODE #	Circum. (cm.)	Mass (g)	Vol (mL)	Density (mass/ vol)	Interior	GEODE #	Circum. (cm.)	Mass (g)	Vol (mL)	Density (mass/ vol)	Interior	GEODE #	Circum. (cm.)	Mass (g)	Vol (mL)	Density (mass/ vol)	Interior
1	13.3	73	35	2.09	Solid	13	8.4	14	5	2.80	Solid	25	9.2	19	9	2.11	Solid
2	12.4	66	25	2.64	Solid	14	12.4	52	23	2.26	Solid	26	13.4	71	31	2.29	Solid
3	11.8	60	22	2.73	Solid	15	12.6	57	24	2.38	Solid	27	7.6	14	7	2.00	Solid
4	12.6	58	27	2.15	Crystals	16	9.0	22	10	2.20	Solid	28	8.7	18	8	2.25	Solid
5	12.0	60	26	2.31	Solid	17	11.6	49	22	2.23	Solid	29	10.6	42	23	1.83	Crystals
6	13.4	73	33	2.21	Crystals	18	12.1	43	20	2.15	Solid	30	12.5	65	30	2.17	Solid
7	13.5	70	35	2.00	Crystals	19	11.1	41	15	2.73	Solid	31	12.2	51	26	1.96	Crystals
8	11.8	49	24	2.04	Crystals	20	8.9	23	11	2.09	Crystals	32	12.7	61	27	2.26	Solid
9	11.5	42	19	2.21	Solid	21	7.7	14	4	3.50	Solid	33	12.9	49	24	2.04	Solid
10	7.8	15	8	1.88	Solid	22	7.3	15	8	1.88	Solid	34	7.4	13	6	2.17	Solid
11	12.7	58	25	2.32	Solid	23	8.2	19	9	2.11	Solid	35	13.1	63	32	1.97	Sandy
12	11.9	43	19	2.26	Solid	24	12.8	46	24	1.92	Crystals	36	13.1	60	25	2.40	Solid

DATA TABLES

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DATA TABLES

GEODE #	Circum. (cm.)	Mass (g)	Vol (mL)	Density (mass/ vol)	Interior	GEODE #	Circum. (cm.)	Mass (g)	Vol (mL)	Density (mass/ vol)	Interior	GEODE #	Circum. (cm.)	Mass (g)	Vol (mL)	Density (mass/ vol)	Interior
36	13.1	60	25	2.40	Solid	49	12.3	67	35	1.91	Sandy	61	11.6	44	25	1.76	Crystals
37	13.6	54	30	1.80	Crystals	50	9.1	18	10	1.80	Solid	62	11.8	43	23	1.87	Solid
38	11.0	38	17	2.24	Solid	51	11.9	51	23	2.22	Solid	63	11.2	41	22	1.86	Solid
39	11.0	41	18	2.28	Solid	52	12.3	58	28	2.07	Solid	64	12.0	50	24	2.08	Solid
40	13.5	57	28	2.04	Solid	53	9.1	20	11	1.82	Sandy	65	12.5	46	20	2.30	Solid
41	13.3	65	28	2.32	Solid	54	12.8	74	33	2.24	Crystals	66	10.9	45	19	2.37	Solid
42	9.8	20	9	2.22	Solid	55	12.1	51	26	1.96	Solid	67	12.2	45	20	2.25	Solid
43	12.0	50	20	2.50	Solid	56	11.8	45	25	1.80	Solid	68	12.1	49	23	2.13	Crystals
44	12.4	32	12	2.67	Solid	57	11.7	59	26	2.27	Solid	69	10.6	37	15	2.47	Solid
45	12.4	49	30	1.63	Solid	58	11.1	44	20	2.20	Solid	70	12.5	55	25	2.20	Solid
46	11.8	42	25	1.68	Crystals	59	9.2	26	10	2.60	Solid
47	12.1	50	25	2.00	Solid	60	13.3	64	30	2.13	Solid
48	11.8	48	26	1.85	Sandy

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Before and After: Images of Geodes and Cracked Open

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Chart A: Crystallized or Solid Geodes

KEY:

CRYSTAL

SANDY INSIDE

SOLID

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Images of our perfect geodes

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CONCLUSION

My hypothesis was correct. The highest density geodes produced only solid rock interiors. The density of all the geodes ranged from 1.63 to 3.50. Of the 70 geodes, only 16 (23%) opened up with the ideal hollowed out center and crystal crusted interior. In Chart A, you can see that nearly 70% of the ideal geodes were clustered in the density range of 1.7-2.0. There were four interesting geodes that looked as if it would have been an ideal type geode with the crystallization but had a sandy/crumbly center rather than hollow. These four geodes also fell in the ideal density range. The solid geodes made up the majority of the results. After a density of 2.15, there were 35 solid geodes that did not have anything inside. In this range, only two opened up to have crystals. Measuring the mass and volume of a geode can allow you to confidentally predict the inside of the geode especially if it will result in a solid rock. The range of 1.7-2 will more than likely give you a nice, crystallized geode.

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Real World Connection

The ability to measure and take data of an object without harming or damaging it is something we try to do in the real world. I was able to measure certain aspects of the geode and with the results of my data, I could predict the inside of the geode without breaking it open. We do this in the medical field when we want to be able to see the inside of people’s organs and cells without doing surgery. This is a useful technique also for very large objects like the Earth. We can take data like earthquake data and try to determine what is on the inside without ever going inside. Being able to do this is important because it is impossible for humans to go to the center of the Earth.