The paper referenced at the bnottom of this page looks at the profits (and losses) made by a large number of Adventurers for each of the seven years for each and every mine in which he held a share.
They did this by multiplying the return for each mine in each year by the adventurer's proportional share in that mine.
This calculation shows 106 adventurers out of a total of 191 sharing a profit of £216,548 over the seven years.
The average gain for each was £2,043, with Sir William Lemon attaining the maximum profit of £26,430.26. Sir William did so well because he held a quarter share in the most profitable of all the Cornish mines at this time, Wheal Unity. You can read more of this family in Brian Elvins' ‘The Lemon Family Interest in Cornish Politics’ in Cornish Studies Seven (1999).
The remaining 85 (of the 191 Adventurers examined here) shared a loss of £37,317 over the same period. The average loss was £439.22, with Messrs Geo C Fox and Sons suffering the greatest loss of £ 4,142.23.
The Fox's held shares in seven mines, Consolidated, Herland, North Downs, Tresavean, Wheal Gorland, Wheal Hope and Wheal Jewell. Of the seven mines only Consolidated Mines (£126.53), and Wheal Jewell (£ 1,338.10) achieved a profit over the seven-year period.
Investing in mines was not the only source of profit to the adventurers. Some were also were mineral lords who did exceedingly well. For example Lord and Lady de Dunstanville, whilst securing a profit of £6,696.42 over the seven years on their holdings in Cook's Kitchen and Wheal Gons & Stray Park, also received a further £9,625 in dues. It is therefore no surprise that: ‘The late Lord de Dunstanville made money, as a landlord, faster from this (i.e. Cook's Kitchen) and the Old Pool Mine than he expended it in building Tehidy House, one of the finest seats in Cornwall’
Guide to Adventurers in Cornwall
Mines and Mining In Cornwall