Fossil Island fossil

Fossils are items on Fossil Island that are used to build displays on the bottom floor of the Varrock Museum (below the natural history floor). Completing a display requires a complete set of one type of fossil (i.e. small/medium/large/rare) and grants 2 kudos and an experience lamp based on the type of category of the fossils. They can be sold to the Fossil Collector in exchange for numulites, or used on the mycelium pool to create enriched bones which can be further processed to eventually gain some Prayer experience.

Obtaining Fossils

Fossils may be obtained from Mairin's Market and from certain actions that roll the fossil drop table.

Every time you roll the fossil drop table, there is a chance you may receive either a fossil, numulite or nothing.

If you receive a fossil, the chance of you receiving each kind of fossil is as follows:

Fossil type	Drop chance
Unidentified small fossil	50%
Unidentified medium fossil	25%
Unidentified large fossil	20%
Unidentified rare fossil	5%

The fossil drop table is as follows:

Actions dropping fossils and numulites
Method	Fossil		Numulite		Nothing
Herbiboar (per trail reveal with experience drop) (About 2.56 rolls per Herbiboar)	7/175	4%	168/175	96%	0/175	0%
Getting fragment from Volcanic mine	5/175	2.9%	35/175	20%	135/175	77.1%
Underwater thieving (per experience drop)	6/175	3.4%	169/175	96.6%	0/175	0%
Bowl of fish	2/175	1.1%	78/175	44.6%	95/175	54.3%
Sulliusceps (per experience drop)	5/175	2.9%	115/175	65.7%	55/175	31.4%
Tar Monster	5/175	2.9%	95/175	54.3%	75/175	42.9%
Hoop Snake	3/175	1.7%	97/175	55.4%	75/175	42.9%
Deranged Archaeologist	12/175	6.9%	163/175	93.1%	0/175	0%
Ammonite Crab	3/175	1.7%	97/175	55.4%	75/175	42.9%
Ancient Zygomite	7/175	4%	143/175	81.7%	25/175	14.3%
Lobstrosity	5/175	2.9%	95/175	54.3%	75/175	42.9%
Lesser Wyvern	10/175	5.7%	165/175	94.3%	0/175	0%
Ancient Wyvern	12/175	6.9%	163/175	93.1%	0/175	0%
Drift net (per fish)	3/175	1.7%	97/175	55.4%	75/175	42.9%
Digging in camp soil	1/175	0.6%	9/175	5.1%	165/175	94.3%

Strategy

This guide makes the assumption that an unidentified large fossil will turn into a large fossil 50% of the time, and a plant fossil 50% of the time.

In order to complete the Varrock museum, you will need approximately 55 unidentified large fossils (95% confidence interval 50-65) in order to get 25 plant fossils and 25 identified large fossils, 60 unidentified medium fossils and 70 small fossils. The rate-limiting step are the unidentified large fossils.

Large fossil gathering
Method	Actions/hour	Drop rate	/hour	Time for 55
Herbiboar	≈70 (82)	7/875 (0.8%)	0.6	98.2 hours
Volcanic mine	?	5/875 (0.6%)	?	?
Underwater thieving +Mairin's Market	110-240	6/875 (0.7%) +shop	1.1-2.4	22.5-49.1 hours
Bowl of fish	Very slow	2/875 (0.2%)	Get fossils from Mairin's Market instead
Sulliusceps	591 (80); 745 (90)	5/875 (0.6%)	3.4; 4.3	16.3 hours 12.9 hours
Tar Monster	Slow	5/875 (0.6%)		Long
Hoop Snake	Slow	3/875 (0.3%)		Long
Deranged Archaeologist	≈30	12/875 (1.4%)	0.4	133.7 hours
Ammonite Crab	162 (72)	3/875 (0.3%)	0.6	99 hours
Ancient Zygomite	137 (114 melee combat)	7/875 (0.8%)	1.1	50.2 hours
Lobstrosity	?	5/875 (0.6%)	?	?
Lesser Wyvern	≈35	10/875 (1.1%)	0.4	137.5 hours
Ancient Wyvern	<≈35	12/875 (1.4%)	0.5	114.6 hours
Drift net	285	3/875 (0.3%)	1	56.3 hours
Camp soil*	1000-3000	1/875 (0.1%)	1.1-3.4	16-48.1 hours

*Extremely click-intensive - 3000 is the theoretical maximum with mousekeys - expect slower rates

Thieving and Mairin's Market

If you are using Mairin's Market, you should save your points and then evaluate the specific fossils you need to achieve your total of 25 plant fossils, 25 large identified fossils and 60 medium fossils.